If someone engages in fornication, sincerely repents to Allah, and resolves not to repeat the act, is the sin forgiven, or does the partner also need to seek forgiveness from the other involved?
Fornication is a major sin. If the person who committed sin sincerely repents and firmly decides not to do it again and seek forgiveness, Allah is The Best Forgiver and The Most Merciful. The partner is responsible for his/her own sin.
Wassalam.