From BiblePortal Wikipedia

Hastings' Dictionary of the Bible [1]

Sackcloth . The sackcloth of OT was a coarse dark cloth made on the loom from the hair of goats and camels. In the extant literature it is almost always associated with mourning for the dead (  Genesis 37:34 ,   2 Samuel 3:31 and oft.): and especially with the public expression of humiliation and penitence in view of some national misfortune, present or impending (  1 Kings 21:27 ,   Nehemiah 9:1 ,   Jonah 3:5 etc.). For other tokens of grief and penitence, associated with the donning of sackcloth, such as ashes or dust on the head, and the rending of garments (this being a later substitute for their entire removal), see Mourning Customs. In such cases the person or persons concerned are generally said to ‘gird’ themselves with sackcloth, or to have sackcloth about their loins, from which it is evident that the sackcloth was worn in the form of a loincloth or waistcloth, tied in the ancient manner in a knot in front (cf.   Isaiah 20:2 ‘loose the sackcloth,’ lit. ‘untie the knot’). It was worn by women as well as by men (  Isaiah 32:11 , Jdt 9:1 ). The putting of it upon cattle, however, as mentioned in   Jonah 3:8 and Jdt 4:10 , and even upon an altar ( Jdt 4:11 ), is, from the nature of the passages cited, rather a literary than a historical extravagance.

In this custom most modern scholars recognize an illustration of conservatism in religious practice. The waistcloth is known to have been the oldest article of dress among the Semites (see Dress, § 2 ), and as such it appears to have been retained in mourning customs and in humiliation before God, and perhaps in the exercise of the cultus, long after it had ceased to be the only garment of the people. The ihram or waistcloth still worn by the Moslem pilgrims during their devotions at the sacred shrine at Mecca, has often been cited as a modern parallel.

A. R. S. Kennedy.

Vine's Expository Dictionary of NT Words [2]

1: Σάκκος (Strong'S #4526 — Noun Masculine — sakkos — sak'-kos )

"a warm material woven from goat's or camel's hair," and hence of a dark color,  Revelation 6:12; Jerome renders it saccus cilicinus (being made from the hair of the black goat of Cilicia; the Romans called it cilicium); cp.  Isaiah 50:3; it was also used for saddle-cloths,  Joshua 9:4; also for making sacks, e.g.,  Genesis 42:25 , and for garments worn as expressing mourning or penitence,  Matthew 11:21;  Luke 10:13 , or for purposes of prophetic testimony,  Revelation 11:3 .

Hawker's Poor Man's Concordance And Dictionary [3]

We read much of the sackcloth with which the prophets and mourners in Zion clad themselves upon occasions of sorrow. Rending the garment, and putting on sackcloth, are terms every where to be met with in the Old Testament. And at any time when a reverse of circumstances took place, they rent the sackcloth from their loins: hence David is represented as saying, "Thou hast turned for me my mourning into dancing; thou hast put off my sackcloth, and girded me with gladness." ( Psalms 30:11) I refer the reader to the word of God for accounts of this apparel. ( Genesis 37:34;  Psalms 35:13;  Isaiah 20:2) There is a prophecy in the book of the Revelations which some think yet remains to be fulfilled, where it is said that the Lord's "two witnesses shall prophecy a thousand, two hundred, and three-score days, clothed in sackcloth?" ( Revelation 11:3) Others suppose the event hath been already accomplished.

Watson's Biblical & Theological Dictionary [4]

a sort of mourning worn at the death of a friend or relation. In great calamities, in penitence, in trouble also, they wore sackcloth about their bodies: "Gird yourselves with sackcloth, and mourn for Abner,"  2 Samuel 3:31 . "Let us gird ourselves with sackcloth; and let us go and implore the clemency of the king of Israel,"  1 Kings 20:31 . Ahab rent his clothes, put on a shirt of haircloth next to his skin, fasted, and lay upon sackcloth,  1 Kings 21:27 . When Mordecai was informed of the destruction threatened to his nation, he put on sackcloth, and covered his head with ashes, Esther 4. On the contrary, in time of joy, or on hearing good news, those who were clad in sackcloth tore it from their bodies, and cast it from them,  Psalms 30:11 . The prophets were often clothed in sackcloth, and generally in coarse clothing. The Lord bids Isaiah to put off the sackcloth from about his body, and to go naked, that is, without his upper garment,  Isaiah 20:2 . Zechariah says that false prophets shall no longer prophesy in sackcloth, to deceive the simple,  Zechariah 13:4 .

Hastings' Dictionary of the New Testament [5]

SACKCLOTH. —A coarse, dark-coloured cloth, made of goat’s or camel’s hair (Gr. σάκκος, Heb. שַׂק), used in ordinary life for sacking, sieves, strainers, and the like, but in the Gospels twice named in connexion with prevalent mourning customs ( Matthew 11:21,  Luke 10:13), coupled with ‘ashes’ (wh. see) as an expression of penitential grief. The mourner wore the sackcloth garment, sometimes next the skin; and because of the garment’s coarseness it became a constant reminder of his grief, its irritation being a sort of penance; sometimes it was worn as an outer garment as a visible expression of mourning. Closely related to this use of sackcloth was the use of it by ascetics and prophets (cf. later use by pilgrims). So John the Baptist wore a garment of camel’s hair ( Matthew 3:4,  Mark 1:6) as the expression of a certain austerity of life, and as a rebuke to the love of ease and luxury which characterized the age.

E. B. Pollard.

People's Dictionary of the Bible [6]

Sackcloth. A coarse black cloth commonly made of hair,  Revelation 6:12, such as that of goats or camels. It was used for straining liquids, for sacks, and for mourning garments. Sometimes it was worn under the ordinary clothes, bound upon the loins, or instead of any other kind of dress; occasionally it was spread on the ground to be lain upon.  Genesis 37:34;  1 Kings 21:27;  2 Kings 6:30;  Isaiah 58:5;  Joel 1:8;  Jonah 3:5-6;  Jonah 3:8. Deep sorrow was hence denoted by sackcloth and ashes.  Matthew 11:21. Such garments were sometimes the dress of prophets and ascetics.  Isaiah 20:2;  Zechariah 13:4.

Bridgeway Bible Dictionary [7]

People put on sackcloth as a sign of mourning, whether for those who had just died ( Genesis 37:34;  2 Samuel 3:31), for some personal distress ( Job 16:15), or for a national disaster ( Esther 4:1;  Lamentations 2:10). They also put on sackcloth as a sign of sorrow for personal sins ( 1 Kings 21:27-29;  Nehemiah 9:1-2) or urgency in prayer ( Daniel 9:3). The sackcloth was worn either over the top of, or instead of, their normal clothing ( 2 Kings 6:30;  Job 16:15;  Jonah 3:6; see Dress ).

Wilson's Dictionary of Bible Types [8]

 2 Samuel 3:31 (b) This is a type of sorrow, grief and mourning. Those who wore this cloth publicly announced that they had broken hearts and sorrowing spirits. (See also1Ki  20:31;  2 Kings 6:30;  Job 16:15;  Psalm 35:13;  Psalm 69:11;  Psalm 32:11;  Jeremiah 4:8;  Daniel 9:3;  Joel 1:13;  Revelation 11:3).

Smith's Bible Dictionary [9]

Sackcloth. Cloth used in making sacks or bags, a coarse fabric, of a dark color, made of goat's hair,  Isaiah 50:3;  Revelation 6:12, and resembling the eilicium of the Romans. It was used also for making the rough garments used by mourners, which were, in extreme cases, worn next the skin.  1 Kings 21:27;  2 Kings 6:30;  Job 16:15;  Isaiah 32:11.

Morrish Bible Dictionary [10]

A rough cloth made of hair, of which sacks and coarse clothing was made. When put on as a symbol of sorrow or repentance it was worn next the skin, and not taken off at night: it was often associated with ashes.  1 Kings 21:27;  2 Kings 6:30;  Job 16:15;  Joel 1:13;  Revelation 6:12; etc.

King James Dictionary [11]

SACK'CLOTH, n. sack and cloth. Cloth of which sacks are made coarse cloth. This word is chiefly used in Scripture to denote a cloth or garment worn in mourning, distress or mortification.

Gird you with sackcloth and mourn before Abner.  2 Samuel 3 .

 Esther 4 .  Job 46 .

Easton's Bible Dictionary [12]

 Genesis 37:34 42:25 2 Samuel 3:31 Esther 4:1,2 Psalm 30:11 Matthew 11:21 Jonah 3:8

Fausset's Bible Dictionary [13]

Of coarse, dark goat's hair. Used for sacks, also for close fitting raiment in mourning; secured by a girdle ( Genesis 42:25;  1 Kings 21:27;  2 Samuel 3:31).

Webster's Dictionary [14]

(n.) Linen or cotton cloth such as sacks are made of; coarse cloth; anciently, a cloth or garment worn in mourning, distress, mortification, or penitence.

Holman Bible Dictionary [15]

 Isaiah 58:5 Jonah 3:8

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [16]

( שִׂק , Sak , from its Net -like or Sieve- like structure; a word which has descended pure in the Greek Σάκκος and modern languages) is the name of a coarse material, apparently made of goat's or camel's hair ( Revelation 6:12), and resembling the Cilicium of the Romans ( Genesis 37:34;  1 Kings 20:31;  2 Kings 19:1 sq.;  Matthew 11:21;  Luke 10:13; comp. Josephus, Ant. 7, 1, 6; Porphyr. Abstin. 4, 15; Plutarch, Superst. c. 7). It was probably dark brown or black in color ( Isaiah 1:3;  Revelation 6:12; comp. The Black Dresses of the Greeks: Eurip. Alc. 440; Orest. 458; Helen , 1088; and Romans, Ovid, Metam. 6, 568; Tacit. Annal. 3, 2; Becker, Gallus, 2, 289; see Josephus, Life, 28). It was used for the following purposes:

(1.) For making sacks for grain, the same word describing both the material and the article ( Genesis 42:25;  Leviticus 11:32;  Joshua 9:4). Sacks are usually made of hair in the East; whence we may understand that where sackcloth is mentioned haircloth is intended.

(2.) This material was certainly employed for making the rough garments used by mourners (Esther 4:21), which were in extreme cases worn next the skin ( 1 Kings 21:27;  2 Kings 6:30;  Job 16:15;  Isaiah 32:11), and this even by females ( Joel 1:8;  2 Maccabees 3:19), but at other times were worn over the coat or Kethoneth (Ton. 3, 6) in lieu of the outer garment. The robe probably resembled a sack in shape, thus fitting closer to the person than the usual flowing garments of the Orientals (Niebuhr, Beschreib. p. 340), as we may infer from the application of the term חָגִר , To Bind , to the process of putting it on ( 2 Samuel 3:31;  Ezra 7:18, etc.). It was confined by a girdle of similar material ( Isaiah 3:24). Sometimes it was not laid aside even at night ( 1 Kings 21:27). Prophets and ascetics wore it over the underclothing, to signify the sincerity of their calling ( Isaiah 20:2;  Matthew 3:4; see Wetstein, N.T. 1, 384 sq.). The Apocrypha intimates that this habit of sackcloth was that in which good people clothed themselves when they went to prayers ( Baruch 4:20). The use of haircloth as a penitential dress was retained by the early Oriental monks, hermits, and pilgrims, and was adopted by the Roman Church, which still retains it for the same purposes. Haircloth was, indeed, called "sackcloth" by the early Greek and Latin fathers. It does not appear that sackcloth is now much used in token of grief in the East; but ornaments are relinquished, the usual dress is neglected, or it is laid aside, and one coarse or old assumed in its place (comp. Liske, De Sacco et Cinere [Vitemb. 1693]). (See Mourning).

Kitto's Popular Cyclopedia of Biblial Literature [17]

The sackcloth mentioned in Scripture was, as it is still in the East, a coarse black cloth, commonly made of hair , and was used for straining liquids, for sacks, and for mourning garments. In the latter case it was worn instead of the ordinary raiment, or bound upon the loins, or spread under the mourner on the ground;;;; ) [MOURNING]. Such garments were also worn by prophets, and by ascetics generally (;; comp.; ).