What is the ruling on supplicating to Allah for concealment (of sins) and fearing that the supplication will not be answered after committing a major sin, especially when there is a young man who wishes to propose marriage and there is a fear of the matter being exposed, knowing that one has returned to Allah and desires a clean life?

Allah is vast in forgiveness and loves those who repent. Allah Almighty says: "Indeed, Allah loves those who repent and loves those who purify themselves." And Allah rejoices greatly at the repentance of His servant, as mentioned in the hadith. Therefore, one should not despair of Allah's mercy. The important thing is the sincerity of repentance and the firm resolve not to return to the sin, along with seeking forgiveness and feeling remorse. And Allah will conceal (the sins of) His servant after his repentance.