Now Jesus was teaching at the temple in Jerusalem early in the morning when those pesky scribes and Pharisees interrupted Jesus with a test to discredit Him in front of the crowd. The scribes and Pharisees unceremoniously tossed a woman accused of adultery into the midst of everyone sitting there, demanding that she be stoned according to the law; but then asked Jesus what He would do. It was an obvious set-up.
Jesus wrote with His finger on the ground as He replied that the one without sin should cast the first stone. Sheepishly they retreated one by one into the shadows without further condemnation of the woman. Jesus conversed with her and then told her to go and sin no more, saying that since her accusers had left, He did not condemn her either (it takes two witnesses).
Of course, this was not going the way the religious leaders had planned; so here they came again and Jesus was ready for them:
Then Jesus spoke to them again, saying, “I am the light of the world. He who follows Me shall not walk in darkness, but have the light of life.” ~ John 8:12 NKJV
Ah-HAH! They thought He was caught red-handed in a blasphemous lie. Jesus was alone and no one there could back up His claims to be the promised Messiah.
The Pharisees therefore said to Him, “You bear witness of Yourself; Your witness is not true.” Jesus answered and said to them, “Even if I bear witness of Myself, My witness is true, for I know where I came from and where I am going; but you do not know where I come from and where I am going. You judge according to the flesh; I judge no one. And yet if I do judge, My judgement is true; for I am not alone, but I am with the Father who sent Me. It is also written in your law that the testimony of two men is true. I am One who bears witness of Myself, and the Father who sent Me bears witness of Me.” ~ John 8:13-18 NKJV
No matter what Jesus told these scribes and Pharisees, they were so blinded to the truth they didn’t know whether they were coming or going; much less believe that Jesus was the promised Messiah. Nor did they know the Father who had sent Him.
Nevertheless, Jesus gave them two witnesses – Himself and the Father. I can’t imagine two greater Witnesses to the truth than Jesus and our Almighty Father God, but it was completely lost on His accusers.