I heard the Messenger of Allah ﷺ say that Allah said, "Son of Adam, as long as you call upon Me and place your hope in Me, I will forgive you whatever is in you, and I do not mind. Son of Adam, were your sins to reach the clouds of the sky and then you sought My forgiveness, I would forgive you, and I do not mind. Son of Adam, were you to come to Me with sins nearly filling the earth and then meet Me without associating anything with Me, I would bring you forgiveness nearly its equal."
سمعت رسول الله ﷺ يقول: قال الله: يا ابن آدم إنك ما دعوتني ورجوتني، غفرت لك على ما كان فيك ولا أبالي، يا ابن آدم لو بلغت ذنوبك عنان السماء، ثم استغفرتني، غفرت لك، ولا أبالي، يا ابن آدم إنك لو أتيتني بقراب الأرض خطايا، لقيتني لا تشرك بي شيئا، لأتيك بقرابها مغفرة.
Tirmidhi (3540) narrated it from Abdullah bin Ishaq Jawhari Basri, who said, Abu Asim narrated to us, Kathir bin Faid narrated to us, Saeed bin Ubayd narrated to us, he said, I heard Bakr bin Abdullah Muzani say, Anas bin Malik narrated to us, and he mentioned it. Then Tirmidhi said, "This is a hasan gharib hadith, we do not know it except from this route."I say, it is as he said, for Saeed bin Ubayd, who is Hinai, is a narrator whose hadith is hasan. As for Kathir bin Faid, no one confirmed him trustworthy except Ibn Hibban, and that is why Ibn Hajar said in Taqrib, "Acceptable," meaning when corroborated, and he has indeed been corroborated.Ibn Shahin narrated it in Targhib (178), and Diya in Mukhtara (4/399), both through the route of Abu Qutayba, Salm bin Qutayba, from Saeed bin Ubayd, with it as a raised hadith. Abu Qutayba Salm bin Qutayba is truthful.