Scripture tells us to establish something, we need to have two to three witnesses. This comes from the following scriptures:
2 Corinthians 13:1
1 This is the third time that I am visiting you. Every fact shall be sustained and confirmed by the testimony of two or three witnesses.
16 But if he does not listen, take along with you one or two others, so that every word may be confirmed by the testimony of two or three witnesses.
15 “A single witness shall not appear in a trial against a man for any wrong or any sin which he has committed; [only] [on the testimony or evidence of two or three witnesses shall a charge be confirmed.
6 On the evidence of two or three witnesses, he who is to die shall be put to death; he shall not be put to death on the evidence of [only] one witness.
And straight from the mouth of Yahushua.
17 Even in your own law it is written that the testimony of two persons is true [valid and admissible]. 18 I am One [of the Two] who testifies about Myself, and My Father who sent Me testifies about Me.”