Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1253
Abdullah b. Abu Qatada reported on the authority of his father: While we said our prayer with the Messenger of Allah (may peace be upon him) he heard tumult. (At the end of the prayer) he (the Holy Prophet) said: What is the matter with you? They said: We hastened to prayer. He (the Holy Prophet) said: Don't do that; when you come for prayer, there should be tranquillity upon you. Pray (along with the Imam) what you can find and complete what preceded you.