Musnad Ahmad 30:3477

Yazid narrated to us, Muhammad ibn Mutarrif informed us, from Zayd ibn Aslam, from ‘Ata’ ibn Yasar, from Abu Hurayrah, from the Prophet, peace and blessings of Allah be upon him, who said: "Whoever goes to the mosque and returns, Allah prepares for him a lodging in Paradise every time he goes and returns."