Why is this episode titled "Book of the Stranger"?

Question

In Game of Thrones, episode 54 of series 6 has been given title Book of the Stranger. How is this title relevant to the episode? What have I missed?

Answer 1

From GoT Wiki:

The Stranger is the aspect of The Seven that represents death. The holy text of the Faith of the Seven is The Seven-Pointed Star, which is divided up into internal books (like the real-life Christian Bible, etc.) - i.e., one internal division is the "Book of the Maiden" (devoted to The Maiden, another aspect of the Seven). The episode takes its name from when Margaery points out that the High Septon is quoting a verse from the Book of the Stranger.

Below is the abovementioned dialogue:

HIGH SPARROW: Of course, but for you, that means seeking out money, finery, power. Seeking out your family means seeking out sin. I’m not maligning you. I sought those things out, too. To the exclusion of all else. My father was a cobbler. He died with I was young and I took over his shop. He was a simple man and he made simple shoes. But I found that the more work I put into my shoes, the more people wanted them. Fine leather, ornamentation, detailing, and time. Time most of all. Dozens of hours spent on a single pair.

MARGAERY: Quality takes time.

HIGH SPARROW: Yes. I imagine you’ve worn a year of someone’s life on your back. The highborn liked to cover their feet with my time and they paid well for the privilege. I used their money to buy a taste of their lives for myself. Each time I indulged, I felt myself ascending to something better.

MARGAERY: And one day you walked through a graveyard and realized it was all for nothing and set out on the path to righteousness. Book of the Stranger, verse 25.

Note that often GoT episode titles match several events/characters. In this case a possible interpretation is that the title is also a reference to Daenerys who in this episode is a stranger that brings death to the Dothraki khals.