Tafsir of Al-Anbiya' 21:72

"And We gave him Isaac..."

Al-Nafilah: The child of a child (grandchild).

It is also said: He asked for Isaac and was granted him, and he was given Jacob as a nafilah—meaning an increase and a bounty without having asked for it.

"And We made them leaders guiding by Our command, and We inspired them to do good deeds, establish prayer, and give zakat; and they were worshippers of Us."