On the authority of Abu Dharr Jundub ibn Junadah, and Abu 'Abd-ir-Rahman Mu'adh bin Jabal (may Allah be pleased with them) that the Messenger of Allah (peace and blessing of Allah be upon him) said:

"Be conscious of Allah wherever you are. Follow the bad deed with a good one to erase it, and engage others with beautiful character."

Related by Tirmidhi