Most translators and commentators agree that verses 16-18 once again introduce the statement of the author of the Gospel and do not continue the words of John the Baptist.
Out of the fullness of his grace he has blessed us all represents the Greek “because from his fullness we all received.” The word fullness was a frequent term among the heretical gnostic religions of the first century A.D. It referred to the full nature of the true deity as opposed to that which did not possess the divine nature. Paul took this term and applied it to God’s Son (see Col 1.19; 2.9; Eph 1.23; and 4.13). However, in John’s Gospel this word is used in a nontechnical sense and refers back to the phrase grace and truth in verse 14. Among the translations, only Good News Translation and Moffatt (“for we have all been receiving grace after grace from his fulness”) appear to make this connection explicit, though a number of commentators call attention to it. In the last part of this clause, the Greek “we all received” is restructured by Good News Translation to read he has blessed us all.
It is dangerous to attempt a literal translation of the clause “from his fullness have we all received.” In one language the people understood it to mean “we got what he stuffed himself on”! In some languages a far better rendering would be “because he was so gracious, he has blessed us all” or “because of his great love for us, he has been so good to us all.”
In this context the use of the pronoun “us” is probably best interpreted as inclusive. Undoubtedly John wrote his Gospel to Christians to whom he wished to explain more fully the significance of the incarnation and ministry of Christ.
Giving us one blessing after another is literally “grace for grace.” The phrase is ambiguous, and some translations (for example, New English Bible “grace upon grace”) prefer to remain ambiguous. The majority of modern commentators take this phrase in the same sense that Good News Translation takes it, that is, that the Christian life consists of one expression of God’s grace after another. Moffatt (“for we have all been receiving grace after grace from his fulness”) and Goodspeed (“received blessing after blessing”) follow this interpretation, and New American Bible (“love following upon love”) seems also to accept this viewpoint. At least two other interpretations are possible, and these are both represented by Jerusalem Bible, one in the text, “grace in return for grace,” and the other in a note, which points out that this phrase may mean that the grace of God revealed in the new covenant in Christ Jesus has now replaced God’s grace as expressed in the old covenant at Mt. Sinai. A third possible interpretation is that the grace of God in the Christian’s life is a result of and grows out of the grace of God in Jesus Christ (see Jerusalem Bible note, “a grace answering to the grace that is in Christ”). This interpretation seems to be the basis for Phillips (“there is a grace in our lives because of his grace”). Of the three interpretations, the first is most widely received, but there is no absolute argument in favor of any of them.
In some languages one cannot speak of giving us one blessing after another, but may use “blessing” as a verb in the sense of “to show goodness to” or “to cause goodness to happen to someone.” If “blessing” is rendered as a verb, it is possible to say “God has blessed us time after time” or “God has caused goodness to happen to us time after time.” In some languages the expression of one blessing after another is rendered “we received good things and still more good things.” In others the rendering is quite idiomatic, for example, “he was big-hearted to us time after time.” In one language this passage has been rendered idiomatically “all of us have received what his heart was full of. This happened many times.” In still another, the rendering is “we received what he has so abundantly; he has looked upon us for good and looked upon us for good more and more,”
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 .