[af_vet_1981]

HOW they transgressed the commandment of YHWH is that 'washing the hands' was not a commandment of YHWH... Do not add to, nor take away from...

I don't think that was the reason. Jerome, who was Fourth Century, explained the ritual washing was from Psalm 26 and he would have been very aware of the story from the gospel.

I will wash mine hands in innocency: so will I compass thine altar, O Lord:

[af_vet_1981]

Correction: Cyril instead of Jerome
I don't think that was the reason. Jerome Cyril, who was Fourth Century, explained the ritual washing was from Psalm 26 and he would have been very aware of the story from the gospel.