Supplication when breaking the fast

Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) narrates: I heard the Messenger of Allah (peace and blessings be upon him) saying: "Indeed, the fasting person has, at the time of breaking his fast, a supplication which is not rejected." Ibn Abi Mulaykah said: I heard Abdullah bin Amr making this supplication at the time of breaking his fast: 'Allahumma inni as'aluka bi-rahmatika allati wasi'at kulla shay'in an taghfira li dhunubi' (O Allah, I ask You by Your mercy which encompasses all things to forgive me my sins).
If the narrator named Ishaq in this chain is the freed slave of Za'idah, then Imam Muslim has narrated from him; and if he is Ibn Abi Farwah, then the two Shaykhs did not narrate from him.

Marwan bin Salim al-Muqaffa' says: I saw Sayyiduna Ibn Umar (may Allah be pleased with them both) grasping his beard in his fist and cutting off whatever exceeded the fist, and he said that when the Messenger of Allah (peace and blessings be upon him) broke his fast, he would recite this supplication: 'Dhahaba al-zama'u, wabtallat al-'uruqu, wa thabata al-ajru in sha' Allah' (The thirst has gone, the veins are moistened, and the reward is established, if Allah wills).
This hadith is sahih on the condition of the two Shaykhs, since both al-Husayn bin Waqid and Marwan bin al-Muqaffa' have been used as evidence.