Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him), while teaching us, used to say: "Do not precede or hasten before the Imam in any action. When the Imam says the takbir, then you also say the takbir; when he bows (for ruku‘), then you also bow; and when he recites « غَيْرِالْمَغْضُوبِعَلَيْهِمْوَلَاالضَّالِيّنَ », then you say Ameen; and when he says « سَمِعَاللهُلِمَنْحَمِدَهُ », then you say « رَبَّنَاوَلَكَالحَمْدُ »; and do not hasten before the Imam in ruku‘ and sujud."
Hadith Referenceصحيح ابن خزيمه / جماع أبواب قيام المأمومين خلف الإمام وما فيه من السنن / 1576