It is narrated from Sayyiduna Yazid bin Rukanah (may Allah be pleased with him) that when the Prophet (peace and blessings be upon him) prayed over the deceased, he would say four takbirs and then say: "O Allah, Your servant and the son of Your female servant is in need of Your mercy, and You have no need to punish him. If he was righteous, then increase his good, and if he was a wrongdoer, then pardon him." Then he would supplicate with whatever he wished.
Hadith Referenceالمعجم الكبير للطبراني / باب الياء / 18867