Musnad Abu Ya'la al-Mawsili 115:353

Ubayd Allah narrated to us, Khalid narrated to us, Sa'id narrated to us, from Qatadah, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) was brought a vessel containing water, enough to cover his fingers or not cover them—Sa'id was in doubt—and they began to perform ablution, and the water began to spring forth from between his fingers. He said: So we said to Anas, "How many were you?" He said, "Three hundred." Khalid said: Then he mentioned a word, then he said, "Three hundred."