Jamieson, Fausset and Brown on Exodus 25:30

30. showbread--literally, presence bread, so called because it was constantly exhibited before the Lord, or because the bread of His presence, like the angel of His presence, pointed symbolically to Christ. It consisted of twelve unleavened loaves, said traditionally to have been laid in piles of six each. This bread was designed to be a symbol of the full and never-failing provision which is made in the Church for the spiritual sustenance and refreshment of God's people.