Musnad Ahmad 30:1686

Isma'il ibn 'Umar narrated to us, he said: Dawud ibn Qays narrated to us, from Musa ibn Yasar, from Abu Hurayrah, who said: "Our dowry, when the Messenger of Allah (may Allah bless him and grant him peace) was among us, was ten awaq." And he clapped his hands together, "And that is four hundred."