Musnad Ahmad 32:556

Yunus narrated to us, Hammad—meaning Ibn Zayd—narrated to us, from Thabit, from Anas or someone else, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever supports two daughters or three daughters, or two sisters or three sisters, until they reach maturity or he dies leaving them behind, I and he will be like these two." And he gestured with his index and middle fingers.