Adam Clarke on Ecclesiastes 5:6

Neither say thou before the angel, that it was an error - Nor think of saying "before the cruel angel, who shall exercise authority over thee in the judgment of the great day, that thou didst it through ignorance." - Chaldee. I believe by the angel nothing else is intended than the priest, whose business it was to take cognizance of vows and offerings. See Lev 5:4, Lev 5:5. In Mal 2:7, the priest is called the "angel of the Lord of hosts."