Imam Malik, may Allah have mercy on him, said: I heard from the people of knowledge, they used to say: There is no harm if a man washes his head with sidr or potash, etc., after throwing pebbles at Jamrah al-Aqabah, before shaving his head, because when he has thrown the pebbles at Jamrah al-Aqabah, it becomes permissible for him to kill lice, shave his head, remove dirt, and wear clothes.
It is narrated from Hazrat Nafi that Sayyiduna Abdullah bin Umar (may Allah be pleased with them) would not wash his head in the state of Ihram, except when he experienced a wet dream.
Hadith Referenceموطا امام مالك رواية يحييٰ / كتاب الحج / 710
Hadith Gradingمحدثین:موقوف صحيح
Hadith Takhrij«موقوف صحيح، و أخرجه البيهقي فى «معرفة السنن والآثار» برقم: 2873، والشافعي فى «الاُم » برقم: 252/7، فواد عبدالباقي نمبر: 20 - كِتَابُ الْحَجِّ-ح: 7»