The Prophet ﷺ said: Complete the front row, then the one that comes next, and if there is any incompleteness, let it be in the last row.
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ أَتِمُّوا الصَّفَّ الْمُقَدَّمَ ثُمَّ الَّذِي يَلِيهِ فَمَا كَانَ مِنْ نَقْصٍ فَلْيَكُنْ فِي الصَّفِّ الْمُؤَخَّرِ