Pastor David preached from Hebrews 6:4-6 with the thought of " When It Is Impossible to be Saved". Doing everything they needed to do as a Jewish Church Member except surrender and accept Christ. Their minds had been enlightened ( see their sin, see the righteousness of Christ, see the judgement to come) tasted of the heavenly gift, felt word of GOD, tasted Holy Spirit. Have come so close but not there. If you keep turning your back then and rejecting the Savior, it will be impossible to be saved.