The “come” of hospitality and the “come” of prayer are isomorphic; in both cases, “come”—like the “yes” of a vow—is addressed to what we cannot see coming. If things had greater clarity and security and a more certain outcome, we would not need to make vows or to pray or, better, we would be unable to, as the vow and the prayer would suffocate with self-complacency.
Both hospitality and prayer say "Come!" to the "perhaps." Both participate in the event by faith.
