Frankincense was placed on the Inner Altar of the tabernacle and burned continuously. The Hebrew word for Frankincense is lebonah, which means incense or free burning. It speaks of intercession. Ps 141:2 “Let my prayer be set before You as incense, the lifting up of my hands as the evening sacrifice.”
Myrrh was used in purification and beautification rites. Spiritually it speaks of suffering and dying to self.
These exotic spices represent the role of Jesus as Priest and Prophet. Song of Solomon 3: 6 “Who is coming in a pillar of smoke, smelling of Myrrh and Frankincense?”