Ishaq bin Mansur al-Kausaj إسحاق بن منصور بن بهرام - الكوسج · The Book on Purification

the Prophet said: "Whoever touches his penis, then he is not to pray until he performs Wudu"

the Prophet met him while he was Junub. He said: " I withdrew - to perform Ghusl. Then he returned, so he said: 'Where have you been?' Or: 'Where did you go?' I replied: 'I was Junub.' So he said: 'Indeed the believer is not defiled.'''