Charles H. Spurgeon on Psalms 141:2

In the gorgeous ceremonial worship of the Hebrews, none of the senses were excluded from taking part in the service...The sense of smell occupied, perhaps, the most prominent place; for the acceptance of the worship was always indicated by a symbol borrowed from this sense: "The Lord smelled a sweet savour." The prayer of the people ascended as incense, and the lifting up of their hands as the evening sacrifice. The offering of incense formed the essential part of the religious service. The altar of incense occupied one of the most conspicuous and honoured positions in the tabernacle and temple... On this altar a censer full of incense poured forth its fragrant clouds every morning and evening; and yearly, as the day of atonement came round, when the high priest entered the holy of holies, he filled a censer with live coals from the sacred fire on the altar of burnt offerings, and bore it into the sanctuary, where lie threw upon the burning coals the "sweet incense beaten small", which he had brought in his hand. Without this smoking censer lie was forbidden, on pain of death, to enter into the awful shrine of Jehovah. Notwithstanding the washing of his flesh, and the linen garments with which he was clothed, tie dare not enter the holiest of all with the blood of atonement, unless he could personally shelter himself under a cloud of incense.

It has been supposed by some writers that incense was invented for the purpose of concealing or neutralizing the noxious effluvia caused by the number of beasts slaughtered every day in the sanctuary. Other writers have attached a mystical import to it, and believed that it was a symbol of the breath of the world arising in praise to the Creator, the four ingredients of which it was composed representing the four elements. While a third class, looking upon the tabernacle as the palace of God, the theocratic King of Israel, and the ark of the covenant as his throne, regarded the incense as merely corresponding to the perfume so lavishly employed about the person and appointments of an Oriental monarch. It may doubtless have been intended primarily to serve these purposes and convey these meanings, but it derived its chief importance in connection with the ceremonial observances of the Mosaic ritual from the fact of its being the great symbol of prayer. It was offered at the time when the people were in the posture and act of devotion; and their prayers were supposed to be presented to God by the priest, and to ascend to him in the smoke and odour of that fragrant offering. Scripture is full of allusions to it, understood in this beautiful symbolical sense. Acceptable, prevailing prayer was a sweet smelling savour to the Lord; and prayer that was unlawful, or hypocritical, or unprofitable, was rejected with disgust by the organ of smell.

Doubtless the Jews felt, when they saw the soft white clouds of fragrant smoke rising slowly from the altar of incense, as if the voice of the priest were silently but eloquently pleading in that expressive emblem in their behalf. The association of sound was lost in that of smell, and the two senses were blended in one. And this symbolical mode of supplication, as Dr. George Wilson has remarked, has this one advantage over spoken or written prayer, that it appealed to those who were both blind and deaf, a class that are usually shut out from social worship by their affliction. Those who could not hear the prayers of the priest could join in devotional exercises symbolized by incense, through the medium of their sense of smell; and the hallowed impressions shut out by one avenue were admitted to the mind and heart by another. The altar of incense stood in the closest connection with the altar of burnt offerings. The blood of the sin offering was sprinkled on the horns of both on the great day of annual atonement. Morning and evening, as soon as the sacrifice was offered, the censer poured forth its fragrant contents, so that the perpetual incense within ascended simultaneously with the perpetual burnt offering outside. Without the live coals from off the sacrificial altar, the sacred incense could not be kindled; and without the incense previously filling the holy place, the blood of atonement from the altar of burnt offering could not be sprinkled on the mercy seat. Beautiful and expressive type of the perfect sacrifice and the all prevailing intercession of Jesus —of intercession founded upon atonement, of atonement preceded and followed by intercession! Beautiful and expressive type, too, of the prayers of believers kindled by the altar fire of Christ's sacrifice, and perfumed by his merits! —Hugh Macmillan, in "The Ministry of Nature," 1871.