Jesus' statements in the Fourth Gospel are never simply "Verily", but "Verily, verily" (25 times).
But the Synoptics (and the rest of the NT) do not know this double use of "Verily", only the single use:
Matthew (32 instances, including prayers)
Mark (15 instances, including long ending of Mark KJV)
Luke (8 instances).
John has a 26th use, his only instance of the single use category, the concluding line of John 21 which is also the conclusion of the Fourth Gospel, a devotional benediction to the work as in prayer.
