Ablution is wajib after touching the penis
Sayyidina Hisham ibn Urwah (SAW) narrated that his father reported from Sayyidah
Busrah bint Safwan (RA) that the Prophet (SAW) said, "If anyone touches his penis then
he must not offer salah till he has performed ablution."
[Ahmed27364, Abu Dawud 181, Nisai 163, Ibn e Majah 479]