24 And again, (the followers of) doctrines, which are instruments of the Evil One, are offended by the word which our Lord spoke, No one has ascended up to heaven but He Who came down from heaven, the Son of Man, Who was in heaven. And they say, “Lo! Our Lord testified that no earthly body has ascended to heaven.” In their ignorance they cannot apprehend the force of this. For when our Lord instructed Nicodemus, he did not apprehend the force of the saying. Then our Lord said to him:— No one has ascended into heaven, so as to come down and relate to you whatsoever is there. For if I have spoken unto you of those things that are in the earth, and you believe not, how shall you believe if I shall speak unto you of those things which are in heaven? For lo! no other witness besides Me has come down from thence, to bear witness concerning those things which are in heaven, so that you should believe. For Elijah went up there, but he came not down along with Me to bear witness, that the testimony of two might be sure.
Source: Demonstrations (New Advent)