For this was how the promise was stated: “At the appointed time I will return, and Sarah will have a son.”
NMVFor this [is] the word of promise, At this time will I come, and Sarah [princess] shall have a son.
OJBFor this word is one of havtachah (promise): KA'ET SHOV ASHUV UL'SARAH BEN (About this time I will come and Sarah shall have a son).
TCENTFor this is what God promised: “About this time next year I will come, and Sarah will have a son.”
T4TYou know that what God promised to Abraham was this: “About this time next year Sarah your wife will bear a son as a result of my enabling [MTY] her to do so.” So Abraham knew that it was not through Ishmael, the son that he already had, that God would fulfill what he had promised him (OR, that his true descendants would come).