Ata' bin Yasar (may Allah have mercy on him) narrates from Sayyiduna Mu'adh (may Allah be pleased with him); he said: I said: "O Messenger of Allah, advise me." He (peace and blessings be upon him) said: "Fear Allah as much as you are able, remember Allah beside every stone and tree, and for whatever evil you do, make a fresh repentance to Allah for it: the hidden (evil) in secret, and the open in the open."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17467