New Defender's Study Bible Notes
11:21 God spared not. Note that God “spared not the angels that sinned” (II Peter 2:4), He “spared not the old world” of the antediluvians (II Peter 2:5), and He “spared not the natural branches” (that is, Israel) when they rejected Him. This verse warns us that He will “also spare not thee” if we do the same. In contrast, however, He “spared not His own Son, but delivered Him up for us all” (Romans 8:32).