A four-year-old boy has died after his Amish mother allegedly threw him in a lake as a sacrifice to God amid a state of 'spiritual delusion'.

Vincen Miller, four, drowned in rural Ohio Saturday after he was tossed into the water at the end of a boat dock at a campground on Atwood Lake.

His mother, whose name has been withheld, is accused of drowning the boy before driving a golf cart carrying her three other kids into the lake, WOIO reports.

The woman, 40, and her husband Marcus Miller believed God was speaking to them and had instructed them to carry out ritualistic tasks to 'prove their worthiness', deputies say.

The couple first jumped off the dock around 1am Saturday as part of the alleged test of faith, but later returned to their campsite, believing they failed to complete the task.