Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "When the prayer is established, come to the prayer in a state of calmness and dignity. Then, whatever part of the prayer you catch, perform it, and whatever you miss, complete it."
Hadith Referenceصحيح ابن خزيمه / جماع أبواب قيام المأمومين خلف الإمام وما فيه من السنن / 1646