Mishkat al-Masabih #674

‘Uthman b. Mazun said, “Messenger of God, grant us permission to become eunuchs." God’s Messenger replied, “He who makes another a eunuch or becomes one himself does not belong to us; fasting serves that purpose among my people." He then said, "Grant us permission to lead the wandering life of the devotee." He replied, "The wandering life of the devotee among my people is jihad in God’s path." He said, "Grant us permission to adopt monkery.” He replied, "Monkery among my people consists of sitting in mosques waiting for the time of prayer." Baghawi transmitted it in Sharh as-sunna.