Musnad Ahmad 32:241

Waki' narrated to us, Salama ibn Wardan narrated to me, he said: I heard Anas ibn Malik say: The Messenger of Allah (peace and blessings of Allah be upon him) said to his companions one day: "Who among you has attended a funeral today?" Umar said: "I." He said: "Who among you has visited a sick person today?" Umar said: "I." He said: "Who among you has given charity?" Umar said: "I." He said: "Who among you has begun the day fasting?" Umar said: "I." He said: "It has become incumbent, it has become incumbent."