Probably what happened was that when the new bread was set out on the Sabbath, they put the cup or spoon on top, and put incense in there, and let it burn until it was consumed. But it was this offering, it says here, an offering made by fire to the Lord, as part of the consecration of the new bread. More than likely, this is what happened.
Symbolically, incense represents a person's reverent allegiance and dependence upon God. And when it is burned, it makes a perfect illustration of prayer. If you would go to Revelation 5:8, you would see, it is told there very specifically, that the incense is the prayers of the saints.
So, what do we do when we pray? Well, we are obviously showing our reverent allegiance and dependence on God, because we affirm to Him that we are of His body, that we are His people, and we ask Him for things. That is what prayer does. And so, incense indicates a person's reverent allegiance and dependence on God.
It is very fascinating to our senses because not only would the smoke go up, but it would also produce a wonderful smell - a balsamic sort of fragrance.
So, the inside of the tabernacle was a fragrant place - it smelled good. Not only was incense burned over the bread, but the incense altar was used both morning and evening showing the prayers of the saints going up before God's throne.
So, here we see the one-on-one nature of David's prayer with God. The incense signifies prayers. And in the New Testament, we find the same picture being portrayed in the throne room portion of Revelation chapters 4 and 5.
So, we are looking at the same figure both in the Old Testament, and the New Testament. The burning of incense represents our prayers before God.
Notice the prayers of the saints - you get the idea of saints in your mind.