Genesis 21:2-3

21:2 So Sarah became pregnant ¹  and bore Abraham a son in his old age at the appointed time that God had told him. 21:3 Abraham named his son – whom Sarah bore to him – Isaac. ² 

Psalms 127:3

127:3 Yes, ³  sons ⁴  are a gift from the Lord,

the fruit of the womb is a reward.

[21:2]  ¹ tn Or “she conceived.”

[21:3]  ² tn Heb “the one born to him, whom Sarah bore to him, Isaac.” The two modifying clauses, the first introduced with an article and the second with the relative pronoun, are placed in the middle of the sentence, before the name Isaac is stated. They are meant to underscore that this was indeed an actual birth to Abraham and Sarah in fulfillment of the promise.

[127:3]  ³ tn or “look.”

[127:3]  ⁴ tn Some prefer to translate this term with the gender neutral “children,” but “sons” are plainly in view here, as the following verses make clear. Daughters are certainly wonderful additions to a family, but in ancient Israelite culture sons were the “arrows” that gave a man security in his old age, for they could defend the family interests at the city gate, where the legal and economic issues of the community were settled.