He (Pbuh) gave glad tidings of forgiveness for what they did before Islam

“When we came back from the Battle of trench, I gathered some men from the Quraysh who knew my status and listened to me. I said to them, ‘You know, by Allah, that I see the affair of Muhammad overpowering all others. I have a suggestion, so what do you think?’ They asked: ‘What is your suggestion?’ I said: ‘I think we should go to An-Najaashi (the Christian ruler of Abyssinia; where the early Muslims migrated to avoid persecution) and stay near him. If Muhammad is victorious over our people, we will be safe with An-Najaashi. For it is better for us to be under his rule than under the rule of Muhammad. But if our people are victorious, then we will only see good from them.’ They said: ‘This is a good suggestion.’ I said to them, ‘Collect a gift for him,’ and the most beloved gift to him from our land was tanned leather. So we gathered many skins for him and then traveled until we reached him. By Allah, we were with him when suddenly ‘Amr ibn Umayyah Adh-Dhamri (a Companion) came, and he had been sent by the Messenger of Allah, sallallaahu ‘alayhi wa sallam, to speak regarding Ja’far and his companions. He entered upon him (An-Najaashi) and then left. I said to my companions, ‘This is ‘Amr ibn Umayyah Adh-Dhamri, if only I enter upon An-Najaashi and ask him to surrender him to me. Then I will strike his neck, and the Quraysh will see that I have exacted revenge by killing the messenger of Muhammad.’ I entered upon him and prostrated to him as I used to do. He said: ‘Welcome, my friend. Have you brought me a gift from your land?’ I said: ‘Yes, O king, we have brought you many leather skins.’ I brought them to him, and he liked and appreciated them. I said: ‘O king, I saw a man leaving (your palace), and he is the messenger of our enemy. Give him to me so I may kill him, for he has killed many of our nobles.’ He became angry, and he put his hand out and struck his nose so hard I thought he had broken it. If the earth split in front of me, I would have entered it out of fear of him. I said: ‘O king, if I had known you would become angry at this, I would never have asked.’ He said: ‘Do you dare ask me to give you the messenger of a man to kill him, a man who receives the same spirit that came to Moses!’ I said: ‘Is he truly as you say, O king?’ He said: ‘Woe to you, ‘Amr! Obey me and follow him. By Allah, he is upon the truth, and he will be victorious over his enemies just as Moses was victorious over Pharaoh and his troops.’ I said: ‘Then give me the oath to Islam.’ He said: ‘Yes’, and then he extended his hand and I gave him the oath of Islam. I went back to my companions when I had changed my opinion from what it was before, and I hid my Islam from them. Then I went to the Prophet of Allah, sallallaahu ‘alayhi wa sallam, to become Muslim (in front of him). I met Khaalid ibn Al-Waleed (this was before the conquest of Makkah) and he was returning from Makkah. I said: ‘Where are you going, Abu Sulaymaan?’ He said: ‘The path has been made clear and that man is a prophet. Go to him and become Muslim, for until when (will you wait)?’ I said: ‘By Allah, I did not come except to become Muslim.’ We went to the Prophet of Allah, sallallaahu ‘alayhi wa sallam, where Khaalid ibn Al-Waleed became Muslim and gave him the oath. Then I came close to him and the Prophet of Allah, sallallaahu ‘alayhi wa sallam, extended his hand out. I said: ‘O Messenger of Allah, I give you the oath on the condition that all my previous sins are forgiven.’ He, sallallaahu ‘alayhi wa sallam, said: ‘O ‘Amr,give the oath, for Islam wipes away what was before it.’ So I gave him the oath and then left..