I committed Zina once in my life and God covered me and nobody know about that, and I feel sorry for what I did and I ask forgiveness from God.I'm going to get married, what if the girl I'm going to marry asked me if I committed adultery before and what if she asked me to swear to God?
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.
Dear brother, as long as Allah has covered you, you must cover yourself with the veil of Allah and do not inform anyone about what you have committed. The Prophet said: "Whoever happens to commit any of these filthy things, should conceal himself with the screen of Allah, and repent to Him, because whoever discloses to us what he committed, we will apply the Ruling of Allah (i.e. the Hadd) on him." [Maalik in Al-Muwatt’a and Al-Bayhaqi in As-Sunan]
The woman you intend to marry does not have any right to ask you about your previous sins as mentioned in your question and you should not answer her as mentioned above.
Allah knows best.
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