The answer
In the church, bells replaced the trumpets of the Old Testament which were used for the following purposes:
When receiving the divine Law. Scripture says, “And when the blast of the trumpet sounded long and became louder and louder, Moses spoke, and God answered him by voice.” (Ex. 19:19). Now bells are rung in the church, being the new Mount Sinai, where the Lord meets His people and speaks to them.
In wars (Judg. 3:27). The church is the arena of spiritual warfare, where the children of God struggle against Satan and against sin by the Holy Spirit, who is their weapon.
When celebrating feasts. We do not cease ringing bells at every service until the last- coming of Christ when we will celebrate an eternal feast and when the sound of God’s trumpet will be heard (1 Thess. 4:16).
When ordaining kings (2 Kings 9:13).
Fr. Tadros Yacoub Malaty