Magna Carta can be read as a historical, constitutional or legal document. But it was first and foremost a religious document. It was sealed by King John in 1215 ‘from reverence for God and for the salvation of our soul and those of all our ancestors and heirs, for the honour of God and the exaltation of Holy Church and the reform of our realm’. The king was acting on the advice of two archbishops and nine bishops. The Charter itself was in many ways the work of Archbishop Stephen Langton. Langton had in his Parisian exile been among the most famous lecturers on the churches’ Old Testament. Moses had commanded in Deuteronomy, that if a king were chosen,

The law, argued Langton, was written down in Deuteronomy to prevent the king from demanding more power than had been agreed. Langton had in particular studied Saul's acclamation as king over Israel: ‘Samuel declared to the people the law of the kingdom and wrote it in a book and deposited it in the presence of the Lord’ (1 Samuel 10:25).

What had been true in ancient Israel was to be true in medieval England. Langton was trying in his contributions to the Charter to realise in England a biblical, covenantal kingship. The Charter would soon be known as the Great Charter of Liberties. It is in the form of a covenant of liberties: a covenant between God, the king and the people, laying down the principles on which the king would reign.