Musannaf Ibn Abi Shaybah 7808 — The ruler who delays the prayer beyond

Sayyiduna Abu Dharr (may Allah be pleased with him) said: My beloved friend, the Prophet (peace and blessings be upon him), instructed me to pray the prayers at their proper times. Then, after you have prayed, if you see that the people have already prayed, your prayer is secured; and if they have not yet prayed, join them, and your prayer will become a voluntary (nafl) prayer.