|Maljis al Jinn "Meeting Place of the Jinn"|
"O Fish, are you constant to the old covenant?"
The proper response is:
"Return, and we return. Keep faith, and so shall we."
It's from the One Thousand and One Nights, specifically the story of the Fisherman and the Genie.
And it's got the feel of an old and ancient ritual in the call and answer.
In The Mummy Returns (2001), a conversation between Medjai Ardeth Bay and Rick O'Connell have a similar call and answer:
If I were to say to you that, "I am a stranger traveling from the East, seeking that which is lost"
And Rick responds:
Then I would reply that, "I am a stranger traveling from the West, it is I whom you seek."
This ritualized call-and-answer is common in many religious and secret society ceremonies. We're all familiar with it.
And putting something like that in a game adds a neat bit for the players, especially if the code phrase is integral to the adventure.
Looking for your own code phrase? Make up your own or you can't get any better than one from The Mysteries of Free Masonry by William Morgan. You can go here for the full, online text. Read it through and find a bit of the ritual that works for you.