Did The Buddha promise to send a Paracelete, or Holy Spirit?

In page 32 of *The Pagan Christ*, Tom Harper writes: "The Buddha, when he prepares to depart, promises (like Jesus) to send the Paraclete, "even the spirit of truth which shall lead his followers into all truth."" I followed the footnote and found the footnote simply adds other information about other claims, but does not refer to the source of the claim. I also googled and didn't find original source material supporting this claim. I think the difficulty is I don't know he exact words to search for. Perhaps a knowledgeable person here would know where this claim comes from.