The reading is from St. Paul's Letter to the Galatians 1:3-10

Brethren, grace to you and peace from God the Father and our Lord Jesus Christ, who gave himself for our sins to deliver us from the present evil age, according to the will of our God and Father; to whom be the glory for ever and ever. Amen. I am astonished that you are so quickly deserting him who called you in the grace of Christ and turning to a different gospel - not that there is another gospel, but there are some who trouble you and want to pervert the gospel of Christ. But even if we, or an angel of heaven, should preach to you a gospel contrary to that which we preached to you, let him be accursed. As we have said before, so now I say again, If any one is preaching to you a gospel contrary to that which you received, let him be accursed. Am I now seeking the favor of men, or of God? Or am I trying to please men? If I were still pleasing men, I should not be a servant of Christ.