Mr. Oliver goes through Sam's contract.

The Contract binds Sam's soul to the Devil. The Contract is a giant book written on parchment-style paper in what appears to be verse form.

Sam manages to get a copy of the Contract after persistent begging of the Devil, and asks his father to look it over. His father tears out pages, and feeds one to the fire, which may reveal the fact that Sam could be the son of the Devil.("What About Blob?") The contract is literally thousands of pages long, which Sam had to sign for three hours to obtain. It is aparrently all in Latin, which Sam cannot understand, but his father can. This gives all the more reason for Mr. Oliver to tear and burn pages, because if Sam can't understand Latin, then there really was no point in taking drastic action to hide the truth.