Sahih Adab al-Mufrad

Sayyiduna Anas and Sayyiduna Malik bin Aws bin Hadthan (may Allah be pleased with them) narrate that the Prophet (peace and blessings be upon him) went out to relieve himself. At that time, he did not find anyone to accompany him, so Sayyiduna Umar (may Allah be pleased with him) followed behind him carrying clods or a water jug. He found the Prophet (peace and blessings be upon him) in a field in the state of prostration, so he moved aside and sat behind him. When the Prophet (peace and blessings be upon him) raised his head, he said: "Umar! You did well that when you found me in prostration, you sat at a distance. Jibreel came to me and said: Whoever sends blessings upon you once, Allah will send ten mercies upon him and raise him by ten degrees."