Hadith: Whoever touches his penis should make ablution

عن عروة قال: دخلت على مروان بن الحكم فذَكَرْنا ما يكون منه الوضوء، فقال مروان: ومن مَسِّ الذَّكَر؟ فقال عروة: ما علمت ذلك، فقال مروان: أخبرتني بُسْرَة بنت صفوان، أنها سمعت رسول الله صلى الله عليه وسلم يقول: «مَنْ مَسَّ ذَكَرَه فليتوضأ».
[صحيح] - [رواه أبو داود والنسائي وابن ماجه]

‘Urwah (may Allah be pleased with him) reported: I once entered upon Marawān ibn al-Hakam, and we discussed the things that, if one does them, he needs to make ablution (ablution). Marawān said: "And touching the penis?" I said: "I do not know about that." Marawān said: "Busrah bint Safwān told me that she heard the Messenger of Allah (may Allah's peace and blessings be upon him) say: 'Whoever touches his penis should make ablution.'"
[Authentic hadith] - [Narrated by Ibn Majah - An-Nasaa’i - Narrated by Abu Daoud]

Explanation

‘Urwah (may Allah be pleased with him) relates that he entered upon Marawān ibn al-Hakam, who was the governor of Madīnah at that time, and they were discussing the things that one is required to make ablution if he did them. In other words, they were studying the things that invalidate ablution. Marawān said: "And touching the penis," i.e. one of the things that nullify one's ablution is touching the penis. ‘Urwah said: "I do not know about that"; i.e. I do not know any proof for this statement, and I do not have knowledge about it from the Messenger of Allah (may Allah's peace and blessings be upon him). Marawān said: Busrah bint Safwān (may Allah be pleased with her) told me that the Prophet (may Allah's peace and blessings be upon him) said: "Whoever touches his penis should make ablution." In At-Tirmidhi's narration: "...he should not pray until he makes ablution." This narration is a clear statement that touching the penis nullifies one's ablution, whether it was touched lustfully or without lust, and whether one intended to touch it or did not intend it, provided that the touching is direct without a barrier (such as clothes) between it and one's hand. If it is touched with a barrier in between, then touching it does not nullify ablution because there was no real touching. Real touching takes place when the skin of one organ (the hand) comes in contact with the skin of the other (the penis). The evidence for that is the following narration of An-Nasā'i and others: "If one of you touches his genitals with his hand and there is no barrier between them, he should make ablution."