Prayer as incense

“May my prayer be set before You like incense; may the lifting up of my hands be like the evening sacrifice.” Psalm 141:2
Frequently throughout the Bible our prayers are spoken of as being like incense (Luke 1:10, Rev. 5:8, Rev. 8:3-4). The incense used in the temple comprised four ingredients: gum resin, onycha, galbanum and frankincense (Ex. 30:34). It was offered every morning and evening, continually rising before the Lord as a sweet-smelling odour (Ex. 30:7-8). Similarly we are encouraged to pray continually (1 Thess. 5:17).
Gum resin is obtained from the myrrh tree; it is the sap that naturally oozes from the tree that is in view here. Onycha is possibly a root or part of a specific shellfish. Galbanum is a dark honey-like substance with an unpleasant odour by itself, but becoming sweet when mixed with the other spices. Frankincense is resin from another kind of tree, obtained by cutting into it.
These all relate to the kinds of prayers that we offer. There are prayers of thanks that we offer to God voluntarily; they are sweet to us as well as to Him. There are also prayers that we offer when we are being crushed and cut down by others, when we are in great pain. Individually these circumstances may not all be sweet-smelling to us, but when combined with all the others, the aroma is pleasing to God. He wants us to have a lifestyle of prayer.