It is narrated from Sayyiduna Wathilah (may Allah be pleased with him) that a man entered the mosque while the Prophet (peace and blessings be upon him) was alone in it, and he (peace and blessings be upon him) moved over a little to make room for him. The man said: "O Messenger of Allah, the place is spacious." the Messenger of Allah (peace and blessings be upon him) said: "A Muslim has a right (over another Muslim)."
Hadith Referenceالمعجم الكبير للطبراني / باب الواو / 18448