Marwan bin Salim al-Muqaffa' said: I saw Ibn Umar (may Allah be pleased with them both), then he narrated the hadith, that when the Messenger of Allah (peace and blessings be upon him) broke his fast he would say: 'Dhahaba al-zama'u wabtallati al-'uruqu wa thabata al-ajru in sha' Allah' ("The thirst has gone, the veins are moistened, and the reward is confirmed, if Allah wills.")
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8133
Mu'adh bin Zuhrah (may Allah have mercy on him) said that it reached him that when the Prophet (peace and blessings be upon him) broke his fast he would say: 'Allahumma laka sumtu wa 'ala rizqika aftartu' ("O Allah, for You I have fasted, and with Your provision I have broken my fast.")
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8134