sincere heart: Under the new covenant, believers have changed hearts (Hebrews 8:10; 10:16; Jer 31:31–34).
in full assurance of faith: Christ's actions for us give us confidence that God will welcome us.
having our hearts sprinkled to cleanse us from a guilty conscience: Christ's sacrificial death has completely cleansed us from sin (see 9:13–14, 19–23).