"Complete the first row, then the one behind it, and if any row is to be left incomplete let it be the last row." (Using translation from Nasāʾī 818)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ أَتِمُّوا الصَّفَّ الْأَوَّلَ ثُمَّ الَّذِي يَلِيهِ فَإِنْ كَانَ نَقْصٌ فَلْيَكُنْ فِي الصَّفِّ الْمُؤَخَّرِ