Fung shui guru turned Christian Peter Chan Chun-chuen was on the point of screaming he was innocent as the judge sent him to jail for 12 years last month.
But Chan says he drew on the strength of his new-found faith and held his tongue.
"As I was about to stand up and scream my innocence out loud, I heard the Holy Spirit tell me to calm down. I struggled in my heart and eventually kept quiet," said Chan, fielding questions from the South China Morning Post through one of his friends who visited him in prison last week.
The day before the July 5 sentencing, Chan had looked shocked and turned red in the face after a jury declared he was guilty of forgery and using a false instrument.
Chan, 53, who went by the name Tony before his religious conversion, had contended he was the lover of late billionaire Nina Wang Kung Yu-sum, head of property developer Chinachem Group and Asia's richest woman, and that she had left him her entire HK$83 billion estate.
He is appealing against both the conviction and sentence. Through his friend, he declined to predict his chances of winning, but said he would preach the word of God once he was free.
"I have become widely known as one of the most unpopular public figures, so I should make use of my special identity to spread the gospel," he was quoted as saying. "I believe many people will be interested in listening to me, which will help me evangelise."
The friend, who passed on Chan's replies to the Post on condition of anonymity, continued: "Peter said life without freedom would be very agonising. But he told me it was a new life arranged by God to give him a new opportunity, so he promised me he would learn to adapt.
"Peter said he had not assessed his chances of winning the appeal, nor had he ever asked God about the outcome. Peter said he simply left it with God, as well as his legal team."
His days in a single cell in Stanley Prison are spent mostly reading and praying. Chan plans to continue his studies in theology, philosophy and English while incarcerated.
"Peter told me his English was so poor that he had obtained an 'H' grade in his secondary school public exam," the friend said. "His son was always teasing him, saying he was the only person in the whole world who could understand his father's English."
Besides studying, he talked to God a lot. "Peter said he had prayed for Ah Kung, hoping she went to heaven," the friend said, using Chan's pet name for Wang.
"During his criminal trial, Chan had heard [Wang's] sister testify that Ah Kung used to go to church when she was young. On hearing that, he had felt relieved as he believed God had taken her to heaven."