Musnad Ahmad 754:1

Waki’ narrated to us, Abu Hilal narrated to us, from Abdullah ibn Sawadah, from Anas ibn Malik, a man from Banu Abdullah ibn Ka’b, who said: The cavalry of the Messenger of Allah (ﷺ) raided us, and I came to him while he was eating lunch. He said: "Draw near and eat." I said: "I am fasting." He said: "Sit, and I will tell you about fasting or the fasting person. Indeed, Allah, the Almighty and Majestic, has relieved the traveler of half of the prayer, and has relieved the traveler, the pregnant woman, and the nursing woman of fasting." [The narrator said]: By Allah, the Messenger of Allah (ﷺ) said both of them, or one of them. Oh, how I regret that I did not eat from the food of the Messenger of Allah (ﷺ).