Musnad Ahmad 1017:116

Waki’ narrated to us, Sa’id ibn Sinan—who is Abu Sinan—narrated to us, from ‘Alqamah ibn Marthad, from Sulayman ibn Buraydah, from his father, who said: The Prophet (peace be upon him) prayed, and a man stood up and said: "Who called for the red camel?" The Prophet (peace be upon him) said: "May you not find it. Mosques were only built for that for which they were built."