Does the first commandment forbid us to honor the saints in heaven? The first commandment does not forbid us to honor the saints in heaven, provided we do not give them the honor that belongs to God alone.
For, behold, henceforth all generations shall call me blessed. (Luke 1:48)
Why do we honor the saints in heaven? We honor the saints in heaven because they practiced great virtue when they were on earth, and because in honoring those who are the chosen friends of God we honor God Himself.
Further reading: CCC 954-959