Silsilat al-Ahadith al-Sahihah

Sayyiduna Abu Ayyub (may Allah be pleased with him) reports that a man came to the Prophet Muhammad (peace and blessings be upon him) and said, "Give me some concise and comprehensive advice." The Prophet (peace and blessings be upon him) said: "When you perform prayer, perform it as if it is your last prayer, and do not say anything for which you would have to apologize tomorrow, and be hopeless (and independent) of what people possess."

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both), he says: A man came to the Noble Prophet (peace and blessings be upon him) and said: O Messenger of Allah! Tell me a hadith, but let it be brief. The Noble Prophet (peace and blessings be upon him) said: "Pray like the person who is bidding farewell (as if it is your last prayer), and pray as if you are seeing Him (Allah). If you cannot see Him, then (at least be sure that) He is seeing you. Lose hope in what people possess, you will live a life of contentment, and avoid those things for which excuses are made."