Mehdi Ameruni, Seyed Bijan Farokhpour Haghigi and Eskander Rezai were arrested at a prayer meeting back in 2012 as part of what's been described as a campaign of intimidation by Iranian authorities against Christians and other religious minorities.
They were charged with "action against national security" and "propaganda against the order of the system" and consequently given sentences of between 1 and 3 years in 2014.
According to the charity Middle East Concern, they've been granted temporary leave from prison. However, they have been led to believe that they will not be summoned to return to prison.
Two other men, Mohammad (Vahid) Roghangir and Massoud Rezai, were arrested at the same time but remain in prison.
Middle East Concern has issued a call for prayer for the situation.
It's calling on Christians to pray that "Mehdi, Seyed and Eskander will quickly recover from their imprisonment, and that they and their families will be strengthened in the Lord and adapt to normal family life.
"That those who remain in prison, including Mohammad and Massoud, will be comforted and released soon.
"That all prisoners in Iran will be treated with respect and dignity as beings created in the image of God and all officials involved will love mercy, act justly, learn about Jesus and choose to follow Him."