From BiblePortal Wikipedia

Bind [1]

(represented by numerous Heb. words). To bind and to loose ( Δέω and Λύω ) are figurative expressions, used as synonymous with Command And Forbid; they are also taken for Condemning and Absolving ( Matthew 16:19). Binding and loosing, in the language of the Jews, expressed permitting or forbidding, or judicially declaring any thing to be permitted or forbidden (comp.  John 20:23;  John 16:13). In the admission of their doctors to interpret the Law and the Prophets, they put a key and a table- book into their hands, with these words; " Receive the power of binding and loosing," to which there seems to be an allusion in  Luke 11:52. (See Lightfoot, Hor. Heb. in loc.) So Christ says, " I am not come to destroy," to unloose or dissolve, " the law, but to fulfil it," that is, to confirm and establish it ( Matthew 5:17). The expression "to bind the law upon one's hand for a sign," etc., is figurative, and implies an acquaintance with it, and a constant regard to its precepts; but the Jews construed the phrase literally, and bound parts of the law about their wrists; hence the custom of wearing phylacteries. Rolls or volumes of writing were tied up; hence the expression in  Isaiah 8:16. (See Phylactery).