The Prophet said: Whoever gives food to a fasting person with which to break his fast, will have a reward equal to his, without it detracting in the slightest from the reward of the fasting person!

Source: Saheeh Targheeb (v. 1, p. 451)

Shaikh al-Islam Ibn Taymiyyah: What’s meant is that he should feed him until he’s satisfied.

Source: al-Ikhtiyaaraat al-Fiqhiyyah (p. 109)