Leviticus 24:7
And thou shalt put pure frankincense upon each row, that it may be on the bread for a memorial, even an offering made by fire unto the LORD. And thou shalt put pure frankincense upon each row, that it may be on the bread for a memorial, even an offering made by fire unto the LORD.
Pure frankincense was set upon each row of the showbread so that it rested on the bread as a memorial, an offering made by fire to the Lord. The showbread itself was made up of twelve cakes laid out in two piles upon the table. That bread was changed out fresh every Sabbath. The loaves taken off the table remained holy and were eaten by the priests.