The symbolic meaning of “burning incense” is indicated in Revelation 8:3-4. Consult the marginal references to this verse.
The solemn feasts - The three great annnual festivals, the Passover, the Feast of Weeks (Pentecost), and the Feast of tabernacles Leviticus 23:4-44; Deuteronomy 16:1-17.
4 Behold, I build an house to the name of the LORD my God, to dedicate it to him, and to burn before him sweetb incense, and for the continual shewbread, and for the burnt offerings morning and evening, on the sabbaths, and on the new moons, and on the solemn feasts of the LORD our God. This is an ordinance for ever to Israel.