From The Didache
, chapter 14.
1 But on the Lord's day, after that ye have assembled together, break bread and give thanks, having in addition confessed your sins, that your sacrifice may be pure.
2 But let not any one who hath a quarrel with his companion join with you, until they be reconciled, that your sacrifice may not be polluted,
3 for it is that which is spoken of by the Lord. In every place and time offer unto me a pure sacrifice, for I am a great King, saith the Lord, and my name is wonderful among the Gentiles.