The mark of earth was seen on the forehead and nose of the Messenger of Allah ﷺ due to the prayer in which he led the people.  

أَنَّ رَسُولَ اللَّهِ ﷺ رُئِيَ عَلَى جَبْهَتِهِ وَعَلَى أَرْنَبَتِهِ أَثَرُ طِينٍ مِنْ صَلاَةٍ صَلاَّهَا بِالنَّاسِ  

The above mentioned tradition has also been transmitted by Ma’mar through a different chain of narrators to the same effect.  

عَنْ مَعْمَرٍ نَحْوَهُ