I am telling you the truth is the same phrase discussed in 1.51.
As in verse 3, so here, Good News Translation inverts the sentence order of the Greek, placing the independent clause before the dependent clause.
Though the expression enter the Kingdom of God appears to have a spatial significance which is not present in see the Kingdom of God (verse 3), there is no essential difference in meaning. Therefore, the same type of expression can be employed in verses 3 and 5. It may be particularly advantageous to use such an expression as “God’s rule” for the Kingdom of God.
The phrase of water and the Spirit (literally “water and spirit” in Greek) offers many difficulties. First, this phrase is substituted for the word again in verse 3, and it may be assumed that John is still speaking of the same topic. However, the mention of “water and spirit” opens an opportunity for a further development of Jesus’ thought. Second, it is not clear just what “water” refers to; and several possibilities have been suggested, of which two are the most widely accepted. Some persons, for example, have suggested that in this context “water” refers to the baptism of John the Baptist or to Jewish purification as a whole, inclusive of the baptism of John, which would be understood as being insufficient, in contrast with that which the Spirit accomplishes. On the other hand, other scholars have seen in this occurrence of “water” a reference to Christian baptism: “water” being the reference to the outward symbol and “Spirit” a reference to the transforming power of God in the life of the believer. Since the phrase is “water and Spirit,” it is important that the two be joined in such a way as not to suggest any contrast.
As indicated above, the phrase is literally “water and spirit,” without a definite article before “spirit.” However, on the basis of verses 6 and 8 (literally “the spirit”) it seems most likely that the Spirit is referred to in this verse. A number of translations make this clear. In fact, the entire context indicates that God’s Spirit is meant. Thus to translate “water and spirit” (Phillips, New English Bible) would be to fail to bring out the real force of the meaning.
Certain serious complications may arise from a literal translation of born of water. In some languages this expression is a specific reference to “afterbirth.” In the present context born clearly refers to the rebirth. Therefore it may be appropriate in some languages to translate “if he is not born again by means of water and by means of the Spirit.” This rendering would be taken to refer to some kind of baptism by water and the transformation produced by the Spirit of God, spoken of as “the baptism of the Spirit.”
It may be important to indicate specifically that the Spirit is “the Holy Spirit.” Otherwise a reader could interpret “not born of water and of spirit” as meaning simply “a person born without any lymph fluid in his body and without any human spirit.”
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 .