New Defender's Study Bible Notes
1:12 know whom I have believed. One who thinks or hopes he or she is a Christian probably is not a real Christian. This greatest of all questions is one whose answer can and should be known! Such verses as I John 5:13 and John 10:27-28, among many others, make this clear. Also see footnotes on I John 2:3 and 5:13.
1:13 sound words. It is vital not only to guard the thoughts but also the very words of Scripture.