Jami at-Tirmidhi 807 (sahih, al-Albani)

قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ مَنْ فَطَّرَ صَائِمًا كَانَ لَهُ مِثْلُ أَجْرِهِ غَيْرَ أَنَّهُ لاَ يَنْقُصُ مِنْ أَجْرِ الصَّائِمِ شَيْئًا ‏"‏ ‏.‏

“Zaid bin Khalid Al-Juhani narrated that:The Messenger of Allah said: "Whoever provides the food for a fasting person to break his fast with, then for him is the same reward as his (the fasting person's), without anything being diminished from the reward of the fasting person”