Musnad Ahmad 1153:410

Khalaf ibn al-Walid narrated to us, al-Rabi’ narrated to us, from Abu Uthman al-Ansari—and he spoke well of him—he said: al-Qasim ibn Muhammad ibn Abi Bakr narrated to me that Aisha said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whatever amount of it causes intoxication when drunk, then a handful of it is forbidden."