the least promising vessel and the gift freely given — "determined to pass on to other…"
determined to pass on to other chronic drug addicts and alcoholics what had been so freely given to him in the E-Tier shower.
Context
The origin story of the novel's second great institution, and its whole ethic in the telling: recovery arrives to a lifelong con in a prison shower as "total self-surrender," and the only response the gift permits is to pass it on. The House exists because a man decided the thing given him for free had to be given away — the least promising vessel imaginable made the vector, which is exactly the doctrine's point.