1 I have heard a reproach, which has greatly vexed me. The unclean (the heathen) say, that this people, which is gathered together out of all nations, has no God. And thus say the impious:— “If they have a God, why does He not avenge His people?” And darkness more exceedingly has thickened upon me, because the Jews also reproach us, and magnify themselves over the children of our people. It happened one day, that a man, who is called wise among the Jews, questioned me, saying:— Jesus, Who is called your Teacher, wrote for you, that If there shall be in you faith like one grain of mustard, you shall say to this mountain, Remove, and it shall remove from before you; and (you shall say) even, Be lifted up and fall into the sea, and it shall obey you. So apparently there is in all your people not one wise man, whose prayer is heard, and who asks of God that your persecutors should cease from you. For clearly it is written for you in that passage, There is nothing which you shall not be able to do.
Source: Demonstrations (New Advent)