Jami' al-Tirmidhi The Book on Fasting al-Hasan bin Atyh bin Njyh الحسن بن عطية بن نجيح Anas ibn Malik a man came to the Prophet and said: “My eyes are bothering me, can I use Kuhl while I am fasting?” He said: “Yes.” https://parallelquran.com/hadith/jami-al-tirmidhi-726/