Musnad Ahmad 32:1301

Muhammad ibn Bakr narrated to us, he said: Sa’id informed us, from Qatadah, from Anas, who said: "A vessel containing water was brought to the Prophet, may Allah bless him and grant him peace, the amount of which would cover his fingers or would not cover his fingers—Sa’id was in doubt—so they began to perform ablution, and the water was gushing forth from between his fingers." He said: We said to Anas: "How many were you?" He said: "Three hundred."