Gevurot Meyruach Hakodesh 1:4-5

And, while gathering them at a yechidus, Moshiach gave instructions to them not to depart from Yerushalayim, but to wait for the havtachah (promise) of [Elohim] HaAv which he said, You heard of from Me. For Yochanan gave a tevilah of teshuva with a mikveh mayim, but you will receive a tevilah in the Ruach Hakodesh not many yamim from now.