other sheep I have ... not of this fold: them also I must bring - He means the perishing Gentiles, already His “sheep” in the love of His heart and the purpose of His grace to “bring them” in due time.
they shall hear my voice - This is not the language of mere foresight that they would believe, but the expression of a purpose to draw them to Himself by an inward and efficacious call, which would infallibly issue in their spontaneous accession to Him.
and there shall be one fold - rather “one flock” (for the word for “fold,” as in the foregoing verses, is quite different).