I was talking with a friend and I remembered a fascinating verse (John 3:36): "Whoever believes in the Son has eternal life; whoever does not obey the Son shall not see life, but the wrath of God remains on him." This verse is powerful in two ways, which I'll now discuss.
First, as some observant folks have pointed out, we see John clearly show the opposite of "believes in the Son" is not "disbelieves the Son," but rather "does not obey the Son." This means that in John's mind, to "believe" and to "obey" are synonymous. This obviously causes problems for the surface-level reading of many Protestants, wherein they think John is advocating a one time act of faith saves you forever. Rather, John is using the verb "believe" and "has" in the Greek Present-Tense, meaning that a person only presently "has" eternal life only so long as he is presently "believing," which is to say he is only saved as long as he is presently "obeying" the Lord Jesus. If the believer stops believing, or stops obeying, the having of eternal life also ceases as well. (See THIS POST to learn about how the Bible defines having Eternal Life, and how Protestants completely misunderstand it. Also THIS POST to see that a person "for whom Christ died" can be lost.)
Second, and more importantly for this post, the verse says that for those who do not believe, "the wrath of God remains on them." This is fascinating because it indicates that everyone (except Adam, Eve, Jesus, and Mary) begins this life with "the wrath of God" upon them by default. Only when a person turns to believing in Jesus does the "wrath of God" stop being on that person. Otherwise, it "remains" on you if you don't accept Jesus. But this means that the "wrath of God" was upon all of us at some point, which is impossible in the Penal Substitution model, since it teaches that Jesus endured the wrath of God in our place. And imagine a person who did not start believing in God until he got to his deathbed, maybe even the "Thief On The Cross" (See THIS POST), this means that the wrath of God was upon them for 99% of their life. Does that make any sense? No. Penal Substitution clearly didn't protect the Good Thief from being under God's Wrath, nor does it for any adult convert for all their prior years. But really, it doesn't matter how long God's Wrath is upon you, what matters is that it could never be upon you per the Penal Substitution claim. This also refutes the minority view among Calvinists which teaches that the Elect are "eternally forgiven" so that they are never born under God's Wrath (which I addressed HERE).