Sayyiduna Samurah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) liked that the Muhajirun and the Ansar should stand close to him (peace and blessings be upon him) in the prayer so that they could learn (the prayer) from him (peace and blessings be upon him).
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6852