Matthew Henry on Leviticus 10

Next to Moses and Aaron, none were more likely to be honourable in Israel than Nadab and Abihu. There is reason to think that they were puffed up with pride, and that they were heated with wine. While the people were prostrate before the Lord, adoring his presence and glory, they rushed into the tabernacle to burn incense, though not at the appointed time; both together, instead of one alone, and with fire not taken from the altar. If it had been done through ignorance, they had been allowed to bring a sin-offering. But the soul that doeth presumptuously, and in contempt of God's majesty and justice, that soul shall be cut off. The wages of sin is death. They died in the very act of their sin. The sin and punishment of these priests showed the imperfection of that priesthood from the very beginning, and that it could not shelter any from the fire of God's wrath, otherwise than as it was typical of Christ's priesthood.

The most quieting considerations under affliction are fetched from the word of God. What was it that God spake? Though Aaron's heart must have been filled with anguish and dismay, yet with silent submission he revered the justice of the stroke. When God corrects us or ours for sin, it is our duty to accept the punishment, and say, It is the Lord, let him do what seemeth him good. Whenever we worship God, we come nigh unto him, as spiritual priests. This ought to make us very serious in all acts of devotion. It concerns us all, when we come nigh to God, to do every religious exercise, as those who believe that the God with whom we have to do, is a holy God. He will take vengeance on those that profane his sacred name by trifling with him.

Do not drink wine or strong drink. During the time they ministered, the priests were forbidden it. It is required of gospel ministers, that they be not given to wine, 1Ti 3:3. It is, Lest ye die; die when ye are in drink. The danger of death, to which we are continually exposed, should engage all to be sober.

Afflictions should rather quicken us to our duty, than take us from it. But our unfitness for duty, when it is natural and not sinful, will have great allowances made for it; God will have mercy, and not sacrifice. Let us profit by the solemn warning this history conveys. When professing worshippers come with zeal without knowledge, carnal affections, earthly, light, vain, trifling thoughts, the devices of will-worship, instead of the offering of soul and spirit; then the incense is kindled by a flame which never came down from heaven, which the Spirit of a holy God never sent within their hearts.