Musnad Ahmad 27:910

Khalaf ibn al-Walid narrated to us, al-Hudhayl ibn Bilal narrated to us, from Ibn Ubayd, from his father, that he sat one day in Mecca and Abdullah ibn Umar was with him. My father said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The likeness of the hypocrite on the Day of Resurrection is like the ewe between two flocks of sheep; if it goes to these, they butt it, and if it goes to those, they butt it." Ibn Umar said to him: "You lied." The people praised my father for good or kindness. Ibn Umar then said: "I do not think of your companion except as you say, but I witnessed the Prophet of Allah (peace and blessings of Allah be upon him) when he said: 'Like the ewe between two flocks.'" He said: "It is the same." He said: "That is how I heard it."