NET
24 This is the disciple who testifies about these things and has written these things, and we know that his testimony is true.
Darby
24 This is the disciple who bears witness concerning these things, and who has written these things; and we know that his witness is true.
KJV
24 This is the disciple which testifieth of these things, and wrote these things: and we know that his testimony is true.