Lyttleton's Comments: Constitutions Clause 15

George Lyttelton (1767). The History Of The Life of King Henry the Second,  Notes to the Second and Third Books.  Sandby and Dodsley. pp. 142-3.

Pleas of debt, whether they be due by faith solemnly pledged, or without faith so pledged, belong to the king's judicature. 

The clergy of England began first in the reign of King Stephen to extend their jurisdiction in the spiritual courts to the trial of persons for breach of faith (pro laesione fidei) in civil contracts by which means they drew thither a vast number of causes which belonged to the civil courts, and of which they had no proper cognisance. To this encroachment they were instigated by the bishops of Rome, and therefore Alexander condemned the above-recited statute, which was made to prevent it.

Contracts in Early English Law
by Frederick Pollock
Harvard Law Review, Vol. 6, No. 8 (Mar. 15, 1893), pp. 389-404
Published by: The Harvard Law Review Association
Stable URL: http://www.jstor.org/stable/1321304

In other words the Constitutions of Clarendon Clause 15 forbade church courts to pass judgement on cases involving the litigation on contracts (principally cases of debt) merely because an oath had sealed the contract. It was the job and jurisdiction of the King's courts and justice to settle matters and issues concerning contracts.

Sir William Blackstone; Edward Christian; Joseph Chitty (1851). Commentaries of the laws of England: in four books; with an analysis of the work. W. E. Dean. pp. 43–.