Witnesses are people who have seen or heard the truth themselves. In that way, only the disciples and the crowds around Jesus were witnesses.
Fortunately, Christ had his message and his deeds recorded by these witnesses. The disciples were either directly or indirectly involved in the writing of the New Testament. The Holy Spirit reminded the disciples of everything that Jesus taught them (John 14:26). The New Testament is the reliable testimony because God inspired it through his Spirit (2 Timothy 3:16). Because we study and believe the true testimony of God, we too today can be witnesses.
17 Mettez-vous en garde contre les hommes; car ils vous livreront aux tribunaux, et ils vous battront de verges dans leurs synagogues;