Sayyiduna Bara’ bin Azib (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) used to come to us (at the time of arranging rows). He would straighten our shoulders and chests with his blessed hand and say:“Your rows should not be crooked, otherwise your hearts will also become crooked. Indeed, Allah the Exalted sends His mercy upon the first row or the first rows, and His angels pray for their forgiveness.”