Urwah narrates from Sayyidah Aishah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) said: "Allah Almighty sends down mercy upon those on the right side of the row, and the angels pray for mercy for them."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5199
Urwah (may Allah have mercy on him) narrates from Sayyidah Aishah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) said: "Allah sends down mercy, and the angels pray for mercy, upon those who join the rows."
So he said in the previous narration; what is preserved with this chain is this wording.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5200
Likewise (through another chain), Husayn bin Hafs narrated it similarly. Abd al-Razzaq and Abdullah bin al-Walid al-Adani also narrated it in the same way from Sufyan. Abu al-Hasan bin Abdan said to me: Abu al-Qasim al-Tabarani said: Both are sahih (authentic).
The Shaykh (al-Bayhaqi) said: He means both chains. As for the text, Mu'awiyah bin Hisham is alone in narrating the first text, so I do not consider it preserved, for Abdullah bin Wahb and Abd al-Wahhab bin Ata narrated it from Usamah bin Zayd with a text like the narration of the group.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5201
Abu Barzah (may Allah be pleased with him) says that the Prophet (peace and blessings be upon him) said to me: "If you are able, stand behind the imam; otherwise on the right side of the row." He said: This is how Abu Bakr and Umar (may Allah be pleased with them both) used to be behind the Prophet (peace and blessings be upon him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5202