The best dhikr is lā ilāha illa Allah (there is no god but Allah), and the best supplication is Alhamdulillah (praise be to Allah)
Jābir (may Allah be pleased with him) reported: I heard the Messenger of Allah (may Allah’s peace and blessings be upon him) say: "The best dhikr is lā ilāha illa Allah (there is no god but Allah), and the best supplication is Alhamdulillah (praise be to Allah)."

