Musnad Ahmad 1153:793

Husayn ibn Muhammad narrated to us, he said: al-Mubarak narrated to us, from al-Hasan, from Sa’d ibn Hisham, who said: I came to ‘A’ishah and said: "O Mother of the Believers, I intend to practice celibacy (tabattul)." She said: "Do not do that. Have you not read: 'There has certainly been for you in the Messenger of Allah an excellent pattern'? The Messenger of Allah (may Allah bless him and grant him peace) married, and children were born to him."