It is narrated from Sayyiduna Shaddad bin Aws (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Soon there will be imams over you who will kill the prayer by delaying it from its times. So pray the prayer at its time, and make your prayer with them a voluntary (nafl) prayer."
Hadith Referenceالمعجم الكبير للطبراني / باب الشين / 7124