The saying ascribed to Christ in an addition to the text after Mark 16:14 in Codex W. This is a late fourth or early fifth century MS of the four gospels discovered in 1906 by C.L. Freer and now in the Freer Museum in Washington. It runs: “And they excused themselves, saying, `This age of lawlessness and unbelief is under Satan, who does not allow the truth and power of God to prevail over the unclean things of the spirits. Therefore reveal thy righteousness now'-thus they spoke to Christ. And Christ replied to them, `The term of years for Satan's power has been fulfilled, but other terrible things draw near. And for those who have sinned I was delivered over to death, that they may return to the truth and sin no more; that they may inherit the spiritual and incorruptible glory of Righteousness which is in heaven.' “ It has some affinity with the general style and content of the longer ending of Mark's gospel as a whole.
See V. Taylor, The Gospel according to St. Mark (1952).