What an odd phrase.
Here, in The Story of King Arthur and His Knights by Howard Pyle, he shows how companions can contain one another and work together.
According to Merlin, Excalibur is an excellent sword: "of so great a temper that he may cut in twain either a feather or a bar of iron." It is powerful and precise, yet it in itself is insufficient.
The scabbard, though, Merlin explains, is where it's at: "his sheath of such a sort that he who wears it can suffer no wound in battle, neither may he lose a single drop of blood."
That's some sort of sheath.
The story continues, but Pyle sums up at the end of the chapter, he shares this fantastic bit of wisdom:
He shows how Faith and Truth work hand in hand ... Faith covers and protects Truth. Faith heals wounds of battle. But Truth, Truth is the shining sword - that two edged sword of the Word of God - that protects and can be wielded with power and precision. The two together are necessary for facing your battles.
In this chapter ... King Pellinor submitted to King Arthur's rule when Arthur used Excalibur for his battle - Pellinor became a useful part of the kingdom. Arthur was defended in his fight from being injured. King Arthur, because of Love, did not destroy Pellinor, but graciously incorporated him into the kingdom where he could use his power rightly.
Maybe that's how Love comes in ... how we wield Faith and Truth.