From BiblePortal Wikipedia

Smith's Bible Dictionary [1]

Ze'dad. (Mountain Side). One of the landmarks, on the north border, of the land of Israel, as promised by Moses,  Numbers 34:8, and as restored by Ezekiel.  Ezekiel 47:15. A place named Sudud exists to the east of the northern extremity of the chain of Anti-Libanus, about fifty miles east-northeast of Baalbec . This may be identical with Zedad.

Hastings' Dictionary of the Bible [2]

Zedad . One of the points mentioned in defining the northern border of the Promised Land in   Numbers 34:8 , and again in Ezekiel’s ideal picture,   Ezekiel 47:15 . The reading is uncertain; not improbably it should be Zerad. The place may perhaps be identified with Khirbet Serâdâ , N. of Abil, E. of Merj ‘Ajûn, towards Hermon.

Fausset's Bible Dictionary [3]

A landmark on the N. of Israel ( Numbers 24:8;  Ezekiel 47:15). Grove conjectures the present Sudud , E. of the N. end of Antilibanus , 50 miles E.N.E. of Baalbek .

Morrish Bible Dictionary [4]

The northern border of the promised land.  Numbers 34:8;  Ezekiel 47:15 . Probably Sudud , 34 23' N, 36 58' E ., about 50 miles E.N.E. of Baalbec.

Holman Bible Dictionary [5]

 Numbers 34:8 Ezekiel 47:15

Easton's Bible Dictionary [6]

 Numbers 34:8 Ezekiel 47:15

International Standard Bible Encyclopedia [7]

zē´dad ( צדדה , cedhādhāh , only found with He4 locale; Samaritan צרדה , cerādhāh  ; Septuagint Σαραδάκ , Saradák , Σαδαδάκ , Sadadák , Σαδδάκ , Saddák ): A town or district named in   Numbers 34:8;  Ezekiel 47:15 as on the ideal northern boundary of Israel. The uncertainty of the reading has led to two different identifications being proposed. The form "Zerad" was accepted by yon Kasteren, and his identification was Khirbet Serada in the Merj ‛Ayun , West of the Hasbany branch of the Jordan and North of ‛Abil . This identification, however, would compel us to draw the ideal boundary along the Qasmiyeh valley and thence eastward to Hermon, and that is much too far South If with Dillmann, Wetzstein, Muehlau and others we read "Zedad," then it is clearly identical with Sadad , a village on the road between Ribleh and Ḳaryetain . It has been objected that Sadad is too far to the East; but here, as in the tribal boundaries also, the references are rather to the district or lands possessed than to their central town or village.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [8]

(Heb. Tsedasd', צַדָד [with. ה directive, Tseda'Dah, צְדָדָה , Slope; Sept. Σαδαδάκ v.r. Σαραδάκ , etc.), one of the landmarks on the north border of the land of Israel, as promised by Moses ( Numbers 34:8) and as restored by Ezekiel ( Ezekiel 47:15). In the former passage it occurs between "the entrance of Hamath" and Ziphron, and in the latter between the "road to Hethlon" and Hamath. A place named Siudud exists to the east of the northern extremity of the chain of Antilibanus, about fifty miles E.N.E. of Baalbek and thirty five S.S.E. of Hums (Robinson, Bibl. Res. 2. 507: Wetzstein, Reis. Ü b. Hauran, p. 88), which Porter thinks is identical with Zedad (Five Years in Damascus, 2, 354356; Giant Cities of Bashan, p. 317); and so also apparently rabbi Schwarz (Palest. p. 26); but the boundaries of Palestine proper never extended so far northward. (See Tribe). A trace of the name possibly lingers in the desert plain called Sahil Judeideh, on the western slope of Antilibanus, in or in ear the district of Zebedany (Robinson, Later Bibl. Res. p. 490).