That is the craziest phrase I have ever heard — “sinned in Adam”!
Babies do not die because they sinned in Adam. All humans die because Adam and Eve’s sin brought a curse of sickness, injury, aging, and death upon all living creatures. Dogs, cats, birds, etc. do not die due to them sinning in Adam.
If you mean humans inherit from Adam and Eve a fallen nature that is prone to sin, okay.
But babies do not sin in Adam or anyone else, they are unable to understand the law of righteousness, and cannot be judged until the age of accountability, when they have a conscience that knows right from wrong. Babies die due to the mortal consequences of the sin nature in them, but not due to “sinning in Adam” or any personal sin committed.
Paul was blameless in terms of the law outwardly, but he still sinned inwardly, as evidenced by his extraordinary zeal for cruelty in putting Christians to death, and his admission that, even when saved, he still was enslaved to sin, and did what he did not want to do.
He says nothing about “sinning in Adam”.
Romans 7
8 But sin, seizing the opportunity afforded by the commandment, produced in me every kind of coveting. For apart from the law, sin was dead. 9 Once I was alive apart from the law; but when the commandment came, sin sprang to life and I died. 10 I found that the very commandment that was intended to bring life actually brought death. 11 For sin, seizing the opportunity afforded by the commandment, deceived me, and through the commandment put me to death. 12 So then, the law is holy, and the commandment is holy, righteous and good….
14 We know that the law is spiritual; but I am unspiritual, sold as a slave to sin. 15 I do not understand what I do. For what I want to do I do not do, but what I hate I do. 16 And if I do what I do not want to do, I agree that the law is good. 17 As it is, it is no longer I myself who do it, but it is sin living in me.18 For I know that good itself does not dwell in me, that is, in my sinful nature. For I have the desire to do what is good, but I cannot carry it out. 19 For I do not do the good I want to do, but the evil I do not want to do—this I keep on doing. 20 Now if I do what I do not want to do, it is no longer I who do it, but it is sin living in me that does it.
21 So I find this law at work: Although I want to do good, evil is right there with me. 22 For in my inner being I delight in God’s law; 23 but I see another law at work in me, waging war against the law of my mind and making me a prisoner of the law of sin at work within me. 24 What a wretched man I am! Who will rescue me from this body that is subject to death? 25 Thanks be to God, who delivers me through Jesus Christ our Lord!
All humans, including babies, do not die because of a curse; they die because they have sinned.
Romans 6:23. For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
Romans 5:18. So then as through one transgression there resulted condemnation to all men, even so through one act of righteousness there resulted justification of life to all men.
The only age of accountability mentioned in the Bible is 20 years old (Numbers 14:29-32) which, of course, has nothing at all to do with the death of babies. Moreover, babies are not judged for their own personal sins—they are judged for the sin that they committed in Adam. Furthermore, babies do not die due to mortal consequences of a sin nature in them (human beings do not have a sin nature); they die because they have sinned—in Adam.
Philippians 3:2. Beware of the dogs, beware of the evil workers, beware of the false circumcision;
3. for we are the {true} circumcision, who worship in the Spirit of God and glory in Christ Jesus and put no confidence in the flesh,
4. although I myself might have confidence even in the flesh. If anyone else has a mind to put confidence in the flesh, I far more:
5. circumcised the eighth day, of the nation of Israel, of the tribe of Benjamin, a Hebrew of Hebrews; as to the Law, a Pharisee;
6. as to zeal, a persecutor of the church; as to the righteousness which is in the Law, found blameless.
Romans 7:14. For we know that the Law is spiritual, but I am of flesh, sold into bondage to sin.
15. For what I am doing, I do not understand; for I am not practicing what I {would} like to {do,} but I am doing the very thing I hate.
16. But if I do the very thing I do not want {to do,} I agree with the Law, {confessing} that the Law is good.
17. So now, no longer am I the one doing it, but sin which dwells in me.
18. For I know that nothing good dwells in me, that is, in my flesh; for the willing is present in me, but the doing of the good {is} not.
19. For the good that I want, I do not do, but I practice the very evil that I do not want.
I do not believe that when Saul of Tarsus believed on the Lord Jesus Christ the consequence was that he became a helpless sinner. Moreover, the man in Romans 7:14-25 is striving with every ounce of his being to keep the Law. This is something that faithful Jews do; it is not is something that faithful Christians do. In Romans 7:14-25 Paul is using a rhetorical device known as “speech in character” that was commonly used by Greek writers in the first century—and so it is today; and not only among Greek writers, but also English writers. Indeed, I have used it several or more times in my posts on the Baptist Board.