Praise be to Allah,
Mu’tamir narrated to us from Humayd [at-Iaweel] fromAnas ibn Maalik who said,
“Allah’s Messenger (peace and blessings be on him) preferred that the Muhaajiroon and the Ansaar stand directly behind him in the prayer.”
(Musnad Ahmad, Vol. 3, p. 100. The isnaad of this h.adeeth is Saheeh according to the conditions set by al-Bukhaaree and Muslim.)
Note:
The Muhaajiroon (the Emigrants) are those converts to Islam who gave support to the at the beginning of the Islamic mission and then migrated with him from Makkah to Madeenah when allowed them to do so. The Ansaar (the Helpers) are the inhabitants of Madeenah who believed in the Prophet (peace and blessings be on him) and gave him shelter and support.
Source:
Thulaathiyyaat Musnad Ahmad ibn Hanbal (may Allah have mercy on him)
Reports of Imaam Ahmad that have only three narrators between him and the Prophet, peace, and blessings be upon him.
Shaykh Muhammad ibn Ahmad ibn Saalim as–Saffaareenee al–Hanbalee ~(1114 –1188 AH)