It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that once he was reciting the Qur'an in the mosque when the Prophet of Allah (peace and blessings be upon him) passed by while he was supplicating. the Prophet (peace and blessings be upon him) had come out (accompanied by) Sayyiduna Abu Bakr and Sayyiduna Umar (may Allah be pleased with them both). When he (peace and blessings be upon him) passed near him, he heard his supplication, while he (peace and blessings be upon him) did not recognize him, and the Messenger of Allah (peace and blessings be upon him) said: "Ask and you will be given." So Sayyiduna Abu Bakr (may Allah be pleased with him) went back to Sayyiduna Ibn Mas'ud and asked: What was the supplication that you made? He said: "I praised Allah and glorified Him." Then he said: "O Allah, there is no god but You; Your promise is true, the meeting with You is true, Paradise is true, Hell is true, Your messengers are true, the prophets are true, and Muhammad (peace and blessings be upon him) is true."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8386