The Brazen Serpent and the Golden Cherubim were not violations of the Second Commandment their Meaning.

The Five Books Against Marcion — Tertullian

Likewise, when forbidding the similitude to be made of all things which are in heaven, and in earth, and in the waters, He declared also the reasons, as being prohibitory of all material exhibition [2963] of a latent [2964] idolatry. For He adds: "Thou shalt not bow down to them, nor serve them." The form, however, of the brazen serpent which the Lord afterwards commanded Moses to make, afforded no pretext [2965] for idolatry, but was meant for the cure of those who were plagued with the fiery serpents. [2966] I say nothing of what was figured by this cure. [2967] Thus, too, the golden Cherubim and Seraphim were purely an ornament in the figured fashion [2968] of the ark; adapted to ornamentation for reasons totally remote from all condition of idolatry, on account of which the making a likeness is prohibited; and they are evidently not at variance with [2969] this law of prohibition, because they are not found in that form [2970] of similitude, in reference to which the prohibition is given. We have spoken [2971] of the rational institution of the sacrifices, as calling off their homage from idols to God; and if He afterwards rejected this homage, saying, "To what purpose is the multitude of your sacrifices unto me?" [2972] -- He meant nothing else than this to be understood, that He had never really required such homage for Himself. For He says, "I will not eat the flesh of bulls;" [2973] and in another passage: "The everlasting God shall neither hunger nor thirst." [2974] Although He had respect to the offerings of Abel, and smelled a sweet savour from the holocaust of Noah, yet what pleasure could He receive from the flesh of sheep, or the odour of burning victims? And yet the simple and God-fearing mind of those who offered what they were receiving from God, both in the way of food and of a sweet smell, was favourably accepted before God, in the sense of respectful homage [2975] to God, who did not so much want what was offered, as that which prompted the offering. Suppose now, that some dependant were to offer to a rich man or a king, who was in want of nothing, some very insignificant gift, will the amount and quality of the gift bring dishonour [2976] to the rich man and the king; or will the consideration [2977] of the homage give them pleasure? Were, however, the dependant, either of his own accord or even in compliance with a command, to present to him gifts suitably to his rank, and were he to observe the solemnities due to a king, only without faith and purity of heart, and without any readiness for other acts of obedience, will not that king or rich man consequently exclaim: "To what purpose is the multitude of your sacrifices unto me? I am full of your solemnities, your feast-days, and your Sabbaths." [2978] By calling them yours, as having been performed [2979] after the giver's own will, and not according to the religion of God (since he displayed them as his own, and not as God's), the Almighty in this passage, demonstrated how suitable to the conditions of the case, and how reasonable, was His rejection of those very offerings which He had commanded to be made to Him.

Footnotes:

[2963] Substantiam.

[2964] Cæcæ.

[2965] Titulum. [See Vol. II. p. 477, this series.]

[2966] Numbers 21:8, 9.

[2967] See John 3:14.

[2968] Exemplum.

[2969] Refragari.

[2970] Statu.

[2971] In chap. xviii. towards the end. [p. 311, supra.]

[2972] Isaiah 1:11.

[2973] Psalm 50:13.