Director of the Awareness Foundation - which promotes peace-building through education - Fr Nadim Nassar, said dialogue must follow the truce.
Fr Nadim, said: "What is going to end the war is - first of all - a ceasefire and then that should be followed by dialogue between the Syrians to find a way forward."
The latest truce, which Russia said was signed by seven major rebel factions in Syria, does not include the Islamic State (IS) group or the al Qaida-affiliated Fatah al-Sham Front.
Warning that groups such as IS could undermine the agreement, Fr Nadim said: "They could create problem, they could open fire at any time, they could break all the rules because they have no rules; they want to dominate Syria."
Minor clashes between troops and rebels in Hama province and Damascus were reported by the Britain-based Syrian Observatory for Human Right, after the ceasefire took effect at midnight on Friday.
It brokered by Russia - which has been providing key military support to Syria's President Bashar Assad - and Turkey, which has long been a sources of supplies and a base for rebels opposed to Assad.
Calling for prayers for Syria, Fr Nadim added: "I want all of us to pray that this ceasefire continues and the negotiations start to end the suffering of the people in a country that has the birthplace of our Lord Jesus Christ."
Click here to listen to Fr Nadim Nassar speaking with Premier's Alex Williams: