William Burkitt on Matthew 26:20

Observe here, The impudent forehead of this bold traitor, Judas, who presumed, as soon as he had sold his Master, to sit down at the table with him, and partake with the other disciples of the solemn ordinance of the passover; had the presence of Judas polluted the ordinance to any besides himself, doubtless our Saviour would never have permitted this bold intrusion.

Learn hence, 1. That nothing is more ordinary than for unholy persons presumptuously to rush in upon the solemn ordinances of God, which they have no right, whilst such, to partake of.

2. That the presence of such persons pollutes the ordinances only to themselves; holy persons are not polluted by the sins of such: for to the pure all things are pure.