And We bestowed on him Isaac and, as an additional gift,(2728) (a grandson), Jacob, and We made righteous men of every one (of them).
2728 Nafilah has many meanings: (1) booty; (2) extra work or prayer; (3) extra or additional gift; (4) grandson. The two last implications are implied here. Not only was Abraham given a son in his old age; he was given not only Isaac (Cf. 19:49), but several sons, the chief being Isma'i1 and Isaac, who both joined in burying him (Gen. 25:9); and he also saw grandsons. Isma'i1 is specially mentioned later (21:85) apart from Isaac's line, on account of his special importance for Islam.