From A. W. Pink’s Exposition of the Gospel of John:
From what has been said, it will be evident that when God told Moses to make a serpent of brass, fix it upon a pole, and bid the bitten Israelites look on it and they should live, that He was preaching to them the Gospel of His grace. We would now point out seven things which these Israelites were not bidden to do.
2. They were not told to minister to others who were wounded, in order to get relief for themselves. This, too, would have appealed to their sentiments as being more practical and more desirable than gazing at a pole, yet in fact it had been most impracticable. Of what use would it be for one to jump into deep water to rescue a drowning man if he could not swim a stroke himself! How then can one who is dying and unable to deliver himself, help others in a similar state. And yet there are many today engaged in works of charity with the vain expectation that giving relief to others will counteract the deadly virus of sin which is at work in their own souls.
Again, Pink hits on the unreasonableness, the impracticality (or in Z’s terminology, irrelevance) of the Gospel.