Majma al-Zawaid — Hadith 856

Mus'ab bin Sa'd narrates: When my father (Sayyiduna Sa'd bin Abi Waqqas (may Allah be pleased with him)) prayed in the mosque, he would keep the prayer short, though he would complete the bowing and prostration; and when he prayed at home, he would make the bowing, the prostration and the prayer long. I said: O father! When you pray in the mosque you keep it short, and when you pray at home you make it long? He said: O my son! We (that is, the Companions) are leaders, and we will be followed.
Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators are the narrators of the Sahih.