I saw Ibn Umar grasp his beard and cut off whatever exceeded a fistful. He said, "When the Messenger of Allah ﷺ broke his fast, he would say, 'The thirst is gone, the veins are moistened, and the reward is confirmed, Allah willing.'"
حدثنا عبد الله بن محمد بن يحيى أبو محمد حدثنا علي بن الحسن أخبرني الحسين بن واقد
رأيت ابن عمر يقبض على لحيته فيقطع ما زاد على الكف وقال كان رسول الله ﷺ إذا أفطر قال ذهب الظمأ وابتلت العروق وثبت الأجر إن شاء الله
Sourcing, its isnad is hasan. Nasai narrated it in Amal al-Yawm wal-Layla, no. 299, and in al-Kubra, no. 10131, from the hadith of Ali bin Hasan bin Shaqiq through this route. Daraqutni graded it hasan, 2/182, and Hakim graded it sahih, 1/422, and Dhahabi agreed with him.