Romans 11:21

Heed - To be careful to consider.

For if God spared not the natural branches - If He, in his infinite justice and holiness, could not tolerate sin in the people whom he foreknew, whom he had so long loved, cherished, miraculously preserved and blessed; take heed lest he also spare not thee. Be convinced that the same righteous principle in him will cause him to act towards you as he has acted towards them, if you sin after the similitude of their transgression; and to this, self-sufficiency and self-confidence will soon lead you. Remember, therefore, the rock whence you were hewn, and the hole of the pit whence ye were digged. Depend incessantly on God's free grace, that ye may abide in his favor.

For if God ... - If God did not refrain from rejecting the Jews who became unbelievers, assuredly he will not refrain from rejecting you in the same circumstances. It may be supposed that he will be quite as ready to reject the ingrafted branches, as to cast off those which belonged to the parent stock. The situation of the Gentiles is not such as to give them any security over the condition of the rejected Jew.

11:21 Be not highminded, but fear - We may observe, this fear is not opposed to trust, but to pride and security.