My friend committed zina with 2 women in the span of 2 years. He's never repeated zina since those years. He regrets his sins and wants to repent. His other friends do know about it, as he has sometimes told them back when he was ignorant. Is the hadd punishment valid for him? Can he marry a chaste woman?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

The prohibition of adultery is confirmed in the Quran, the Sunnah, and the consensus of all the scholars of the Muslim nation. Its prohibition is known in religion by necessity. Still, if your friend is in a state in which he can be excused for his ignorance because he is a newcomer to Islam, for example, and likewise, then the sin is lifted from him, and the punishment is not carried out on someone like him, but he must be careful in the future.

Assuming that he was in a state in which there is no excuse for him, then whoever repents, Allah will accept his repentance, and he does not have to confess for the Hadd (corporal punishment determined in Islam) to be inflicted on him. This is with the knowledge that the establishment of punishments is the responsibility of the Muslim ruler and not the general public. The conditions for sincere repentance are abandoning the sin, regretting what has passed, and resolving not to repeat it in the future.

The repentant fornicator (or adulterer) is permitted to marry a chaste woman, and marriage is Islamically required, which may be obligatory, in the case of those who fear for themselves falling into Zina (fornication or adultery). In any case, one should hasten to it, as it is one of the good things, as Allah Says (what means): {…So race to [all that is] good…} [Quran 02:148]

We forewarn that whoever is afflicted with falling into sin (whether minor or major) must cover his sin up and not tell anyone about it. Abu Hurairah said: “I heard the Messenger of Allah saying, “Every one of my followers will be forgiven except those who expose (openly) their wrongdoings. An example of this is that of a man who commits a sin at night, which Allah has covered for him, and in the morning, he would say (to people): “I committed such and such sin last night,' while Allah had kept it a secret. During the night Allah has covered it up but, in the morning, he tears up the cover provided by Allah for himself”. [Al-Bukhari and Muslim]

Allah knows best.