Musnad Ahmad 2:307

Waki’ narrated to us, ‘Umar ibn al-Walid ash-Shanni narrated to me, from ‘Abdullah ibn Buraydah, who said: ‘Umar sat in a place where the Messenger of Allah (peace and blessings of Allah be upon him) used to sit, and funerals would pass by him. He said: They passed by a funeral and praised it with good, so he said: "It has become incumbent." Then they passed by a funeral and praised it with good, so he said: "It has become incumbent." Then they passed by a funeral and spoke good of it, so he said: "It has become incumbent." Then they passed by a funeral and said: "This was the greatest liar among the people." He said: "Indeed, the greatest liar among the people is the one who lies about Allah, then those who follow them, from those who lie about his soul in his body." He said: They said: "What do you see if four testify?" He said: "It has become incumbent." They said: "And three?" He said: "It has become incumbent." They said: "And two?" He said: "It has become incumbent, and for me to have said one is more beloved to me than red camels." He said: It was said to ‘Umar: "Is this something you say based on your own opinion, or something you heard from the Messenger of Allah (peace and blessings of Allah be upon him)?" He said: "No, rather I heard it from the Messenger of Allah (peace and blessings of Allah be upon him)."