It is narrated from Hazrat Amr (may Allah be pleased with him) that I submitted in the presence of the Messenger of Allah, "O Messenger of Allah! (peace and blessings be upon him) I pledge allegiance to you on the condition that all my previous sins are forgiven." The Prophet (peace and blessings be upon him) said, "Islam wipes out all the sins that came before it, and migration also wipes out all the sins that came before it." He says that I was more modest before the Prophet (peace and blessings be upon him) than anyone else, so I never looked at him with full eyes, nor did I ever argue with him in my desires, until he met Allah, the Exalted.
Hadith Referenceمسند احمد / مسند الشاميين / 17813
Hadith Gradingحکم دارالسلام:الشطر الأول منه حسن، وهذا الإسناد ضعيف، ابن لهيعة سيئ الحفظ ، وقيس بن سمي- على الصواب- ليس بمشهور