This verse is similar to verse 16 in that it draws a conclusion on the basis of the previous scripture quotation, so then.

Makes stubborn is literally “harden.” The Revised Standard Version and Jerusalem Bible render this with the sense of “to harden (someone’s) heart.”

As in the case of verse 15, the clauses whom he wishes may be translated as conditional since in a sense these clauses are conditional relatives—for example, “whomever he wishes.” Therefore, one may translate as “if God wishes to show mercy on someone, he does so, and if he wishes to make someone stubborn, he does that.”

Normally it is wise to avoid the idiom “to harden the heart.” Even in European languages in which this phrase has been translated literally, the correct meaning of the Semitic idiom (which is basically “to make stubborn or obstinate”) has not been accurately represented. Furthermore, in some languages “to harden the heart” would mean “to make a person brave,” and this is obviously wrong.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on Paul’s Letter to the Romans. (UBS Handbook Series). New York: UBS, 1973. For this and other handbooks for translators see here .