Sunan an Nasai 188
The Book of Purification
أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا يَحْيَى، قَالَ حَدَّثَنَا سُفْيَانُ، عَنِ الأَغَرِّ، - وَهُوَ ابْنُ الصَّبَّاحِ - عَنْ خَلِيفَةَ بْنِ حُصَيْنٍ، عَنْ قَيْسِ بْنِ عَاصِمٍ، أَنَّهُ أَسْلَمَ فَأَمَرَهُ النَّبِيُّ صلى الله عليه وسلم أَنْ يَغْتَسِلَ بِمَاءٍ وَسِدْرٍ .
It was narrated from Qais bin 'Asim that he accepted Islam, and the Prophet commanded him to perform Ghusl with water and lotus leaves
Grading: Abu Ghuddah: Sahih · Al-Albani: Sahih · Zubair Ali Zai: Sahih
Text from the public-domain hadith-api dataset. Numbering follows that dataset and can differ by a few from some printed editions — check the wording, not only the number.