Jesus answered is literally “Jesus answered and said to him,” reflecting once again Semitic redundancy in introducing direct discourse.

The pronouns you … I are emphatic; so also is the phrase what I am doing.

You will understand later is literally “but you will understand after these things.” The phrase “after these things” is vague, but it may refer to when Jesus had been raised to glory (12.16; see also 2.22). That is, only after Jesus’ death and resurrection will the disciples realize the full meaning of what he is now doing.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .