963. hadíth
قَالَ زُرَارَةُ سَمِعْتُ أَبَا جَعْفَرٍ عَلَيْهِ اَلسَّلاَمُ يَقُولُ: «اَلدُّعَاءُ بَعْدَ اَلْفَرِيضَةِ أَفْضَلُ مِنَ اَلصَّلاَةِ تَنَفُّلاً.
Zurarah reported that he heard Abu Ja'far (a.s) say: "Supplication after the obligatory prayer is better than offering a voluntary prayer." And thus, this has been the practice.