Malik ibn Aws ibn al-Hadathan said, "The Prophet, (ﷺ), went out to open ground to answer a call of nature and did not find anyone to follow him. 'Umar went out and followed him with a clay pot or wudu' vessel. He found him prostrating in a river bed. He fell back and sat behind him until the Prophet, (ﷺ), lifted his head. He said, 'You have done well, 'Umar. When you found me prostrating, you went behind me. Jibril came to me and said, 'If someone says the prayer on you once, Allah will pray ten times on him and raise him ten degrees.'"

حَدَّثَنَا أَبُو نُعَيْمٍ، قَالَ‏:‏ حَدَّثَنَا سَلَمَةُ بْنُ وَرْدَانَ قَالَ‏:‏ سَمِعْتُ أَنَسًا، وَمَالِكَ بْنَ أَوْسِ بْنِ الْحَدَثَانِ، أَنَّ النَّبِيَّ صلى الله عليه وسلم خَرَجَ يَتَبَرَّزُ فَلَمْ يَجِدْ أَحَدًا يَتْبَعُهُ، فَخَرَجَ عُمَرُ فَاتَّبَعَهُ بِفَخَّارَةٍ أَوْ مِطْهَرَةٍ، فَوَجَدَهُ سَاجِدًا فِي مِسْرَبٍ، فَتَنَحَّى فَجَلَسَ وَرَاءَهُ، حَتَّى رَفَعَ النَّبِيُّ صلى الله عليه وسلم رَأْسَهُ فَقَالَ‏:‏ أَحْسَنْتَ يَا عُمَرُ حِينَ وَجَدْتَنِي سَاجِدًا فَتَنَحَّيْتَ عَنِّي، إِنَّ جِبْرِيلَ جَاءَنِي فَقَالَ‏:‏ مَنْ صَلَّى عَلَيْكَ وَاحِدَةً صَلَّى اللَّهُ عَلَيْهِ عَشْرًا، وَرَفَعَ لَهُ عَشْرَ دَرَجَاتٍ‏.‏