A 27-year-old suspect has been arrested over the murder of a man burnt alive in a city park.
The suspect, an Irishman, is being questioned at Finglas Garda Station where he can be held for 24 hours.
Detectives have identified the victim, who is also an Irish national and believed to be in his 40s.
He was violently beaten before being set alight in a sleeping bag.
The grim discovery was made by gardai near the Wellington monument in Phoenix Park in the early hours of Friday.
He called on Christians to be awake and attentive to where society is slipping into wrong ways.
In his homily at the Church of Saint Andrew on Westland Row, Dublin, Archbishop Martin said nations are still raising weaponry against others.
"In our own city how often do we read about knives being raised in violence and guns in vengeance and lives - young lives - being ruined?" he asked the congregation at a mass marking the first Sunday of advent.
"Like you, I am horrified to see in our world of progress and enlightenment that men and women and children are driven in their hundreds of thousands from the homes through wars as in Syria.
"Like you, I am horrified by the news of someone being burned alive in the Phoenix Park in these days.
"Christians in our society must find the ways to speak up and stand up as witnesses to the God of peace and loving care.
"Advent, then, is a moment in which we should interrupt our daily life and think about what is essential."