Overconfidence and a false sense of security would lead to the same disastrous results that the Jews had experienced. Compare Heb. 4:1.

 Or, “Stop thinking high things,” that is, Do not be conceited. The Gentile Christian has no more merit of his own than had the Jews, who were cut off. Therefore, he has no reason to be conceited. Moreover, faith cannot live in the man whose “soul ... is lifted up” (Hab. 2:4).

 Paul goes on to correct the false inference expressed in the preceding verse, by reminding the Gentile Christians of how they had become members of spiritual Israel. The Jews had been cast off because of their unbelief. The Gentiles had been accepted because of their faith. When the true cause of Israel’s rejection is recognized, it leaves no occasion for the Gentile Christian to boast. It is, rather, a warning to hold fast to his faith as the sole condition on which he remains safe as a branch in the tree. Therefore, he should not be “highminded” because of his new privileges and position, but rather he should beware lest he fall as others have fallen. See on chs. 3:3; 10:17.

Gr. apistia, “lack of faith.” Compare the word pistis, translated “faith” in the next clause. The close relationship between these two words is clearly seen in the Greek.

 Gr. kalōs, “that is true,” “granted” (cf. Mark 12:32). Paul admits the truth of the statement that branches were broken off, with the result that others were grafted in.