Because of the importance of incense, only priests were allowed to offer it. So incense is in a higher position than prayer because prayer can be raised by any individual to the Lord. When Korah, Dathan and Abiram dared to offer incense, the earth opened its mouth and swallowed them with all their belongings. So they went down to the pit alive (Num.16: 31,32). This happened not because they offered a sacrifice, but because they offered incense, even though they were of the tribe of Levi.