Sayyiduna Nu’man bin Bashir (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) used to straighten the rows, until he would make them like an arrow or a spear. When he saw someone’s chest protruding forward, the Prophet (peace and blessings be upon him) would say: O servants of Allah! Straighten your rows, or Allah the Exalted will create discord among you.