Sunan an-Nasa'i, Volume 1, Book 5, Hadith 467 (DarusSalam) ⓘ

It was narrated from Abu Hurairah that the Prophet said: "The first thing for which a person will be brought to account on the Day of Resurrection will be his Salah. If it is found to be complete then it will be recorded as complete, and if anything is lacking He will say: 'Look and see if you can find any voluntary prayers with which to complete what he neglected of his obligatory prayers.' Then the rest of his deeds will be reckoned in like manner."

أَخْبَرَنَا أَبُو دَاوُدَ، قَالَ حَدَّثَنَا شُعَيْبٌ، - يَعْنِي ابْنَ زِيَادِ بْنِ مَيْمُونٍ - قَالَ كَتَبَ عَلِيُّ بْنُ الْمَدِينِيِّ عَنْهُ - أَخْبَرَنَا أَبُو الْعَوَّامِ، عَنْ قَتَادَةَ، عَنِ الْحَسَنِ، عَنْ أَبِي رَافِعٍ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ ‏ "‏ إِنَّ أَوَّلَ مَا يُحَاسَبُ بِهِ الْعَبْدُ يَوْمَ الْقِيَامَةِ صَلاَتُهُ فَإِنْ وُجِدَتْ تَامَّةً كُتِبَتْ تَامَّةً وَإِنْ كَانَ انْتَقَصَ مِنْهَا شَىْءٌ قَالَ انْظُرُوا هَلْ تَجِدُونَ لَهُ مِنْ تَطَوُّعٍ يُكَمِّلُ لَهُ مَا ضَيَّعَ مِنْ فَرِيضَةٍ مِنْ تَطَوُّعِهِ ثُمَّ سَائِرُ الأَعْمَالِ تَجْرِي عَلَى حَسَبِ ذَلِكَ ‏" ‏ ‏.‏