In Hebrews 4, verse 11 forms the “backdrop” for verse 12’s description of God’s word (“living and powerful, sharper…a discerner of the thoughts and intents of the heart”). When we recognize the point the Holy Spirit is making in verse 11, then we can appreciate the actual lesson in verse 12: Christians are supposed to “be diligent” (NKJ) about entering the “rest” God has prepared for us! To the Jewish Christians who first read this letter, the word “rest” corresponded to their ancestors’ image of the promised land, and the inspired writer’s application here is, “DON’T make the same mistake as those who died in the wilderness because their disbelief led to disobedience!” (cf. 3:18-19 & 4:2).
The actual lesson in Hebrews 4:11-13 is for Christians to realize that OUR (eternal) “promised land” likewise depends on OUR obedient faith – and that faith must be rooted in God’s word. Jesus told His disciples in John 6:63 that, “The words that I speak to you are spirit, and they are life.” That same basic thought is present here in verse 12, as the word of God “measures” our thoughts and motives. Christians cannot plead ignorance in judgement because the Holy Spirit has provided us all the “answers” for our “final exam!” Therefore nothing about us can be concealed or hidden from God, because His word has defined every aspect of the right way for us to both live in the present world AND prepare for eternity.
One of the greatest blessings God has provided for Christians is to have Someone to stand between us and Him, Who can relate fully to all our trials and temptations in this life. Our high priest is better than those who served in the Jerusalem temple, not just because He is sinless (Hebrews 4:15, cf. Leviticus 16:6 & 11), but also because He doesn’t just enter the Father’s presence one day a year – He lives there forever! Christians should NOT, therefore, feel that our Father is unapproachable, because the “person” at His right hand is there to “stand FOR” US! This is why WE can be bold about bringing our worries, our cares, and our concerns directly to our Father, Ephesians 3:11-12. Because we have such a high priest, we can (we have!) “overcome the world” (1 John 5:4), and therefore should have NO fear in taking our prayers and requests directly to Him in our prayers (1 John 5:14 & Philippians 4:6).