Abdel hamid Kishk tells story of a man who repented and the mercy of Allah is shown. It is stated in Quran:

'Surely Allah loves those who turn much (to Him), and He loves those who purify themselves." - Quran, Sura 02 (Al-Baqara), ayah 222

The religion of Islam does not require you to purchase anything, make sublimation to anyone. If you have a sin, all Quran stated is you turn to Allah and repentant!