وَعَن قيس بن عَاصِم
أَنَّهُ أَسْلَمَ فَأَمَرَهُ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: أَنْ يَغْتَسِلَ بِمَاءٍ وَسِدْرٍ
When he accepted Islam the Prophet (sallallahu alayhi wa sallam) commanded him to bathe with water and lote-tree leaves. Tirmidhi, Abu Dawud and Nasai transmitted it.