Tafsir of Al-Anbiya' 21:72

ووهبنا له إسحق ويعقوب نافلة

And We bestowed upon him Ishaq, and Ya`qub Nafilatan. Ata' and Mujahid said, "Nafilatan means as a gift.'' Ibn Abbas, Qatadah and Al-Hakam bin `]Uyaynah said, "The gift of a son who has a son,'' meaning that Yaqub was the son of Ishaq, as Allah says:

فبشرنها بٳسحق ومن ورآء إسحق يعقوب

But We gave her glad tidings of Ishaq, and after Ishaq, of Yaqub. (11:71) Abdur-Rahman bin Zayd bin Aslam said, "He asked for one (son), and said,

رب هب لى من الصلحين

"My Lord! Grant me from the righteous.'' (37:100) So Allah gave him Ishaq, and gave him Yaqub in addition.

وكﻼ جعلنا صالحين

Each one We made righteous. means, both of them were good and righteous people