If they call you a liar, tell them infinite is the mercy of your Lord; but His vengeance will not be turned back from the sinners.
But the idolaters say: "If God had so willed we would not have associated (others with Him), nor would have our fathers, nor would we have forbidden any thing." So had others denied before them, and had to taste Our punishment in the end. Ask them: "Have you any knowledge? Then display it. You follow nothing but conjecture, and are nothing but liars."
Say: "To God belongs the consummate argument. Had He willed He would surely have guided all of you aright."
Tell them: "Bring your witnesses to testify that God has forbidden this (and this)." Then even if they testify, you should not testify with them; and do not follow the wishes of those who deny Our signs and believe not in the Hereafter, and make others the equal of their Lord.
Tell them: "Come, I will read out what your Lord has made binding on you: That you make none the equal of God, and be good to your parents, and do not abandon your children out of poverty, for We give you food and We shall provide for them; and avoid what is shameful, whether open or hidden, and do not take a life which God has forbidden, unless for some just cause. These things has God enjoined on you. Haply you may understand.