Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates that the Prophet (peace and blessings be upon him) said: "Allah Almighty says: O son of Adam, offer two rak'ahs for My sake in the early part of the day, and I guarantee you until the last part of it (the day)."
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains Layth bin Abi Sulaym, and he is a mudallis (one who commits tadlis).