There is a lesson to be learned in the pope's final hours of suffering, the Archbishop of Armagh has said.
Dr Brady said Pope was "great teacher of the Church"
Vatican officials said Pope John Paul II's heart and kidneys are failing, he is suffering from low blood pressure and his breathing is shallow.
Speaking on Friday, Dr Sean Brady said the ailing pontiff had a special place in the affection of Irish Catholics.
The pontiff was given the Catholic sacrament for the sick and dying - called the Anointing of the Sick.
"The Holy Father has endured a lot of suffering in his life, right from his earliest years when he lost his mother and his only brother," said the archbishop.
"He has been a man who has been educated at the school of sacrifice and suffering, but his suffering in recent times has been purely inspirational.
"The way he has faced all this illness with serenity, with courage, with a deep faith and I think that is probably his last and one of his finest lessons."
Presbyterian Moderator Ken Newell said the pope would be remembered for his efforts to build peace in Northern Ireland.
"People who are close to him and people who have also read his writings realise that he carries the people of Northern Ireland, both Protestant and Catholic, in his heart," he said.
People gathered at the Vatican at news of the Pope's worsening health
Former Church of Ireland Bishop of Derry and Raphoe Dr James Mehaffey said the Pope could relate to people regardless of age or denomination.
"He went on these grand tours worldwide, met people and I have reflected about him often and I think he set a great example to all of us, especially those ordained," he said.
Former Bishop of Derry Father Edward Daly said he provided many with inspiration.
"He didn't hide away he appeared in front of people in all his brokenness," he added.
Irish Prime Minister Bertie Ahern said the thoughts of everyone were with the pope in his failing health.
"It's not just sad for Catholics, it's sad for people generally," he said.
"I wonder would all the changes have happened in eastern Europe had he not been there for the last quarter of a century, I don't think they would have."
Pope John Paul II made Ireland the third pilgrimage of his 26-year pontificate when he visited for three days in September and October 1979.
He made an impassioned plea for peace in Northern Ireland, but did not visit there.
Last year, the Irish Bishops' Conference said he accepted in principle an invitation to return again.