I can’t keep track of the names of musical modes, so I put this Modes summary together from several sources.

In 1399, after John of Gaunt died, the king disinherited Gaunt’s son, Henry of Bolingbroke, who had previously been exiled. Henry invaded England in June 1399 with a small force that quickly grew in numbers. Claiming initially that his goal was only to reclaim his patrimony, it soon became clear that he intended to claim the throne for himself.

“My gracious lord, I come but for mine own.”
Henry Bolingbroke, The Tragedy of King Richard II, Shakespeare, 1597, Act 3, Scene 3

“He asketh nought but that is His.”
Christmas Carol: Now May We Singen as it Is, Trinity Roll, 1420

 The Trinity Roll is a collection of carols including “Deo Gracias Anglia”, the Agincourt Carol. It is a scroll of parchment housed in Trinity College, Cambridge (Manuscript O.3.58).  It was written about 1420, the year that King Henry concluded the Treaty of Troyes and became regent and heir apparent to the French throne, and then married Catherine of Valois.

 “Deo Gracias Anglia” is obviously written to praise the King. Was “Now May We Singen as it Is” also written to praise the King’s father Henry IV by making a comparison to Christ? The carol begins:

This babe to us that now is born,
Wonderful works He hath ywrought,
He would not lose what was forlorn,
But boldly again it bought;
And thus it is,
For sooth I wis,
He asketh nought but that is His.

 And later:

His ransom for us hath ypaid.
Good reason have we to be His.

 So, the carol says directly that Christ ransomed us so we should serve him. Since He has already paid the price, “He asketh nought but that is His.”

 The story of Henry Bolingbroke coming for what already belonged to him was well enough known 200 years later that it was included in the play. Wouldn’t it have been known 20 years later? Was this such a common phrase and concept that two similar references in 20 years is unsurprising, or is the lyricist intentionally echoing the famous story about the King’s father?

I don’t think we have enough information to prove it either way, but it is interesting.