Rev Barry Trayhorn, who resigned from HMP Littlehey Prison, said his treatment after he spoke about forgiveness during a chapel service made it impossible for him to return to work.
An Employment Tribunal ruled the ordained Pentecostal minister had spoken about forgiveness in an "insensitive" way, which ""failed to have regard for the special nature of the congregation in the prison".
During a service, Mr Trayhorn quoted 1 Corinthians 6:9-11 which talks about the forgiveness of sins including adultery and homosexuality.
HMP Littlehey houses sex offenders.
Days after the service in May 2014, he was stopped from participating in future chapel ceremonies.
Several complaints were later raised about his conduct as a gardener at the prison which accumulated in him being handed a final written warning.
He had worked as a gardener at the prison since May 2011 and volunteered in some chapel services since 2012. He resigned in November 2014.
Mr Trayhorn is challenging the decision at an Employment Appeal Tribunal, with the support of the Christian Legal Centre.
Commenting before Thursday's hearing, Mr Trayhorn said: "Prisoners need to hear God's word just as much as anyone else. If people come to a Christian chapel service, we cannot hold back the gospel truth that God forgives those who repent.
"As I led the worship, I spoke about the wonder of God's love and the forgiveness that comes through Jesus Christ to those who recognise their sin and repent. I said that I am the worst sinner I know.
"But the prison decided that wasn't a politically correct message. The mere mention of homosexual behaviour in the Bible verses that I quoted provoked complaint. It is the Bible which is really on trial."