Sayyiduna Abu Mas'ud Uqbah bin Amr (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) would straighten our shoulders with his hand when forming rows for prayer and would say: "Stand straight and do not differ, lest your hearts differ among you." Sayyiduna Abu Mas'ud (may Allah be pleased with him) says that today you have fallen into severe disagreement. This is the narration of Waki'. In the narration of Abu Usamah and Ibn Abi 'Adi, it is stated that the Prophet (peace and blessings be upon him) would align our shoulders, and in the narration of Muhammad bin Ja'far, it is mentioned that the Prophet (peace and blessings be upon him) would pass his hand over our shoulders (and align them).