The transitional adverb now, which begins this verse, must not be understood in a temporal sense. It is equivalent in some languages to “but note that.”
Verse 16 is judged by some as a parenthetical elaboration of verse 15, since verse 15 can be connected in a natural manner with verse 17. What connects verse 16 with verse 15 is the word “promises,” which now supplants the word “covenant.” Since God’s covenant with Abraham consisted of promises, this substitution is appropriate (see Eph 2.12).
Promises is plural in the Greek, the reference apparently being to the repeated occasions on which the promise was made to Abraham, and the various forms in which it was expressed (Gen 12.2 ff.; 13.14 ff.; 15.1,5,18; 17.2 ff.). Elsewhere Paul uses the singular form (for example in verses 17, 18, 22, 29; Rom 4.13,14,16,20), and it seems that to him there is no marked difference of meaning between the singular and the plural. It is in this light that some translators (for example Phillips) render “promises” in the singular. It is even possible to avoid the problem of number altogether by converting the noun into a verb: “God promised….” Or one may introduce something of the plural meaning by translating “God promised on various occasions,” or “… repeatedly.”
It is important in this first sentence of verse 16 to employ a form which will clearly identify only one of Abraham’s descendants. This is necessary if Paul’s interpretation of the scripture passage is to be meaningful. Therefore, one may have to translate “God repeatedly promised to Abraham blessing to him and to one of his descendants.” In some languages it would be impossible to say “promised to Abraham and to one of his descendants,” since the promise was made specifically to Abraham and the blessing simply applied to one of his descendants. The promise itself was not made specifically to one of the descendants since the descendant had not been born at the time that the promise was made.
The scripture does not use is literally “(it) does not say” (the subject is missing in the Greek). It is even possible to understand “God” as the subject. Most translators and commentators, however, understand “scripture” as the implicit subject of the sentence (see Jerusalem Bible, New American Bible, Phillips).
The real exegetical problem in this verse is in Paul’s use of “descendant” and “descendants” (literally, “seed” and “seeds”). Although he was certainly aware that the Hebrew and Greek forms of the word “seed” are singular in form but collective in meaning, yet he goes on to distinguish between the singular and the plural in order to prove his point, namely, that the promises of God were given to Abraham and one descendant, not many; and that one descendant is Christ. Some scholars have found rabbinical parallels to Paul’s exegetical method in this verse, and other interpreters have used ingenious ways to justify Paul’s reasoning here. Fortunately, the translator does not have to hold to a particular position regarding these verses in order to translate them accurately.
In some languages it may be necessary to render the second sentence of this verse as “The scripture does not have the words ‘and to your descendants’ (that is, talking about many people).” Likewise, the following sentence may have to begin “but the scripture has the words ‘and to your descendant.’ ” However, in some other languages there is a problem in the expression “and to your descendant,” since this might imply that Abraham had only one descendant. For that reason it may be necessary to say “and to one of your descendants.” Accordingly, the final explanation in this verse may be rendered as “these words refer to only one person, and that person is Christ.”
Quoted with permission from Arichea, Daniel C. and Nida, Eugene A. A Handbook on Paul’s Letter to the Galatians. (UBS Handbook Series). New York: UBS, 1976. For this and other handbooks for translators see here .