Surah 21. Al-Anbiya, Ayah 72

I.e., in addition (nafilatan) to his eldest son Ishmael (Isma'll) who had been born years before Isaac.

Nafilat has many meanings: (1) booty; (2) extra work or prayer; (3) extra or additional gift; (4) grandson. The two last significations are implied here. Not only was Abraham given a son in his old age; he was given not only Isaac, but several sons, the chief being Isma'il and Isaac, who both joined in burying him (Gen. xxv. 9); and he also saw grandsons. Isma'il is specially mentioned later (xxi. 85) apart from Isaac's line, on account of his special importance for Islam.