«كان يحب أن يليه المهاجرون والأنصار في الصلاة ليحفظوا عنه»
It was the practice of the Prophet (peace and blessings be upon him):
"He (peace and blessings be upon him) liked the Muhajirun and the Ansar to stand close to him in prayer, so that they could remember the prayer from him."
Hadith Referenceصحیح الجامع الصغیر / حرف الكاف / 4924