What is the supplication that Abu Bakr, may Allah be pleased with him, asked the Messenger of Allah, may Allah’s peace and blessings be upon him, to say in his prayer?

The supplication mentioned is what was reported in the Two Sahihs and other collections from Abdullah ibn Umar, from Abu Bakr (may Allah be pleased with them both), that he said to the Messenger of Allah (peace and blessings be upon him): "Teach me a supplication that I may say in my prayer." He (the Prophet) said: "Say: 'O Allah, I have wronged myself with great wrongdoing, and none forgives sins except You. So forgive me with a forgiveness from You, and have mercy upon me. Indeed, You are the Forgiving, the Merciful.'"