"The first thing for which a person will be brought to account will be his Salah. If it is complete (all well and good), otherwise Allah will say: 'Look and see if My slave did any voluntary prayer.' If he is found to have done voluntary prayers, his obligatory prayers will be completed therewith."
عَنْ رَسُولِ اللَّهِ ﷺ قَالَ أَوَّلُ مَا يُحَاسَبُ بِهِ الْعَبْدُ صَلاَتُهُ فَإِنْ كَانَ أَكْمَلَهَا وَإِلاَّ قَالَ اللَّهُ ﷻ انْظُرُوا لِعَبْدِي مِنْ تَطَوُّعٍ فَإِنْ وُجِدَ لَهُ تَطَوُّعٌ قَالَ أَكْمِلُوا بِهِ الْفَرِيضَةَ