Is it obligatory to tell a suitor about a fiancée's past, or is repentance and not telling him sufficient?

Your friend erred by informing your fiancé about your past relationship, from which you have repented, because a Muslim is commanded to conceal the faults of their brother. What your friend did is not a religiously obligatory act of advice, for no one has the right to mention a bad past from which its owner has repented. Your husband has excused you and accepted you after learning of your repentance and uprightness, and in doing so, he has acted correctly, for "the one who repents from sin is like one who has no sin." Do not initiate a conversation with your husband about this matter, and if he asks you, tell him it was a fleeting relationship that you regretted and repented from. Do not fear the past as long as you have repented and become upright, and ask Allah for success and acceptance of your repentance. For Allah is forgiving to those who repent, believe, do good deeds, and then are guided.