Musnad Ahmad 913:3

Muhammad ibn Ja‘far narrated to us, he said: Shu‘bah narrated to us, from Hisham ibn ‘Urwah, he said: My father narrated to me, from the reliable from the reliable—meaning by his saying: "the reliable from the reliable," Abu Ayyub, from Ubayy ibn Ka‘b: "From the Messenger of Allah, may Allah bless him and grant him peace, regarding the one who approaches his wife, then does not ejaculate: he washes his private part and performs ablution." ‘Abdullah said: My father said: "The reliable from the reliable [means] a trustworthy person from a trustworthy person."