15. As for Sarai thy wife God now promises to Abraham a legitimate seed by Sarai. She had been (as I have said) too precipitate, when she substituted, without any command from God, her handmaid in her own place: Abraham also bad been too pliant in following his, wife, who foolishly and rashly wished to anticipate the design of God; nevertheless, their united fault did not prevent God frown making it known to them that he was about to give them that seed, from the expectation of which, they had, in a manner, cut themselves off. Whence the gratuitous kindness of God shines the more clearly, because, although men impede the course of it by obstacles of their own, it nevertheless comes to them. Moreover, God changes the name of Sarai, in order that he may extend her preeminence far and wide, which in her former name had been more restricted. For the letter י ( yod) has the force among the Hebrews of the possessive pronoun: this being now taken away, God designs that Sarah should every where, and without exception, be celebrated as a sovereign and princess. (410) And this is expressed in the context, when God promises that he will give her a son, from whom at length nations and kings should be born. And although at first sight this benediction appears most ample, it is still far richer than it seems to be, in the words here used, as we shall see in a little time.
(410) Sarah shall her name be. Heb., שרה, Sarah. Sarai properly signifies “my princess,” as if sustaining that relation to a single individual or to a family. The restriction implied in the possessive “my” is now to be done away: her limited pre-eminence is to be unspeakably enlarged. Thus, instead of “my princess,” she is henceforth to bear an appellation importing “princess of a multitude,” and corresponding with the magnificent promise made to her, ver. 16. — Bush, Notes on Genesis