Musannaf Ibn Abi Shayba 3:2288

Abu Bakr narrated to us, he said: Abbad bin al-Awwam narrated to us, from Musa al-Hanafi, from Mus'ab bin Sa'd, that he narrated, saying: My father, when he prayed in the mosque, would lighten the bowing and the prostration and would hasten. And when he prayed in his house, he would lengthen the bowing, the prostration, and the prayer. So I asked him [about that], and he said: "We are leaders who are followed."