Musnad Ahmad 80:0

Narrated by Abd al-Rahman ibn Khanbash: The Prophet (peace be upon him) said: "I saw my Lord, the Blessed and Exalted, in the best form." He said: "He said: 'O Muhammad!' I said: 'Here I am, my Lord, at Your service.' He said: 'What do the Highest Assembly (the angels) dispute about?' I said: 'I do not know, my Lord.' He placed His hand between my shoulders until I felt the coolness of His fingertips between my breasts—or he said: 'in my chest'—and everything between the east and the west became clear to me. He said: 'O Muhammad! What do the Highest Assembly dispute about?' I said: 'About the expiations (kaffarat).' He said: 'And what are they?' I said: 'Walking to the congregational prayers, sitting in the mosques after the prayers, and performing ablution (wudu) thoroughly during difficulties.' He said: 'And what else?' I said: 'Feeding others, speaking gently, and praying at night while the people are asleep.'"