Whenever the Prophet ﷺ took the bath of Janaba (sexual relation or wet dream) he asked for the Hilab or some other scent. He used to take it in his hand, rub it first over the right side of his head and then over the left and then rub the middle of his head with both hands.  

كَانَ النَّبِيُّ ﷺ إِذَا اغْتَسَلَ مِنَ الْجَنَابَةِ دَعَا بِشَىْءٍ نَحْوَ الْحِلاَبِ فَأَخَذَ بِكَفِّهِ فَبَدَأَ بِشِقِّ رَأْسِهِ الأَيْمَنِ ثُمَّ الأَيْسَرِ فَقَالَ بِهِمَا عَلَى رَأْسِهِ