﴿ وَجَعَلْنَٰهُمْ أَئِمَّةًۭ يَهْدُونَ بِأَمْرِنَا وَأَوْحَيْنَآ إِلَيْهِمْ فِعْلَ ٱلْخَيْرَٰتِ وَإِقَامَ ٱلصَّلَوٰةِ وَإِيتَآءَ ٱلزَّكَوٰةِ ۖ وَكَانُوا۟ لَنَا عَٰبِدِينَ ﴾

“and made them leaders who would guide [others] in accordance with Our behest: for We inspired them [with a will] to do good works, and to be constant in prayer, and to dispense charity: and Us [alone] did they worship.”

وَوَهَبْنَا لَهُ إِسْحَاقَ وَيَعْقُوبَ نَافِلَةً (And We blessed him with Ishaq and Ya` qub as gift - 21:72) That is, Allah Ta` la had bestowed upon him the son Ishaq (علیہ السلام) as per his supplication and in addition to that a grandson Ya` qub (علیہ السلام) as a gift. This is why he is referred to as نَافِلَةً nafilah which originally means 'extra'.