From the Canon of Dordt:
“Hence it clearly appears that some have acted very improperly and against all truth, fairness, and love in wishing to persuade the public of the following:
…Many innocent children of believers are torn from their mothers’ breasts and tyrannically thrown into hell, so that neither the blood of Christ nor their baptism nor the prayers of the church at their baptism can be of any help to them.”
From hence-you can see that even Reformed Christians (second generation from the Protestant Reformation) believed that infant baptism has some utility in securing the salvation fo their children. It is also adduced that in ther story of David and his child with Bathsheba- that “I shall go to him, but he will not return to me.” meaning that this child -being his child- a child of the covenant is in a saved condition. This is always offered as a proof of child salvation based on the covenant.
But does it also mean that the child was alrerady covenantally circumcised? The child died on the 7th day-As per Matthew Poole reckoning-it is reckon from the date of the child’s birth. The Hebrew words used is na’ar and yeled -both indicating a child from infancy to early adolescent-there is no indication that it is definitely a 7- days old baby. But if it is a 7-days old baby-then it had never reached the 8th day. And what is the 8th day means?
Genesis 17:12 And every male among you who is eight days old shall be circumcised throughout your generations, a servant who is born in the house or who is bought with money from any foreigner, who is not of your descendants.
Which means that David still thinks that the child-since he is a covenant child- is secure in God’s hand-even without the benefit of a covenantal sign and seal! And that those Christians parents who have children who dies in infancy need not fear if their children did not receive the sacrmanent of baptism in order to be sure of their children’s salvation.
Well it is debateable at the least-but I still think that if we believe in the omniscience of our God and that the example of Jesus in holding children as good examples of citizens of the kingdom-We need not fear from thie Middle Age superstition. Our Father protects his children-and his Son’s death at the cross infinite worth is able to ransom them from the fiery hell awaiting the devil and his angels.