It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: O son of Adam, act with the thought that someone is watching you, consider yourself among the dead, and beware of the supplication of the oppressed.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 8522
Hadith Gradingحکم دارالسلام:حدیث قابل للتحسین، و إسنادہ ضعیف لضعف علي ، ولجھالة الواسطة بینه و بین أبي ھریرۃ