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The Canons of Dordt

The First Main Point of Doctrine
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Article 17: The Salvation of the Infants of Believers

Since we must make judgments about God's will from His Word, which testifies that the children of believers are holy, not by nature but by virtue of the gracious covenant in which they together with their parents are included, godly parents ought not to doubt the election and salvation of their children whom God calls out of this life in infancy.

Romans 8:29 (in Arminian): For whom He foreknew, He also [foreknew] to be conformed to the image of His Son, that He might be the firstborn among many brethren.