Abdullah bin al-Samit reports from Sayyiduna Abu Dharr (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "What will you do when rulers over you delay the prayers from their times?" or he said: "will let the time of the prayers pass?" I said: "What do you (peace and blessings be upon him) command me?" He (peace and blessings be upon him) said: "Pray the prayer at its time; if you catch the prayer with them, it will be a voluntary prayer for you."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5315