Moreover, the Father judges no-one, but has entrusted all judgment to the Son,

“the Father judges no-one”, etc. That is to say, the Father does not act in judgment without the Son, nor the Son without the Father, for in no work is either isolated from the other.  (McGarvey TFG 202)

The Father, the Judge, has exercised His prerogative of judging through His Son.  The next verse shows us why.