1 “Moreover, you shall make an altar as a place for burning incense; you shall make it of acacia wood. 2 “Its length shall be a cubit, and its width a cubit, it shall be square, and its height shall be two cubits; its horns shall be of one piece with it. 3 “You shall overlay it with pure gold, its top and its sides all around, and its horns; and you shall make a gold molding all around for it. 4 “You shall make two gold rings for it under its molding; you shall make them on its two side walls–on opposite sides–and they shall be holders for poles with which to carry it. 5 “You shall make the poles of acacia wood and overlay them with gold. 6 “You shall put this altar in front of the veil that is near the ark of the testimony, in front of the mercy seat that is over the ark of the testimony, where I will meet with you. 7 “Aaron shall burn fragrant incense on it; he shall burn it every morning when he trims the lamps. 8 “When Aaron trims the lamps at twilight, he shall burn incense. There shall be perpetual incense before the LORD throughout your generations. 9 “You shall not offer any strange incense on this altar, or burnt offering or meal offering; and you shall not pour out a drink offering on it. 10 “Aaron shall make atonement on its horns once a year; he shall make atonement on it with the blood of the sin offering of atonement once a year throughout your generations. It is most holy to the LORD.”
Strange incense was a big deal to God. Later on, the priest Eli would have two sons that disregarded this instruction, and they offered impure/unholy incense on the altar. What did God do? He struck them dead. God wants us to be pure before Him. We may not always be perfect, but we must make sure our hearts and lives are pure before we come to Him.