Hebrews 4:12
For God's word is alive and active and sharper than any double-edged sword. It penetrates [deep enough] even to divide [a person's] soul [from his] spirit, and his joints [from his] bone marrow [Note: This is figurative language describing the penetrating effect of God's word into a person's spiritual, inner being] and is able to judge the thoughts and intentions of a person's heart.
Hebrews 12:15-16
Look carefully [at how you are living] so that no one falls away from God's unearned favor, and that no "poisonous plant sprouts up" to cause trouble and corrupt many people [Note: This is an analogy from Deut. 29:16-18 being used as a warning against the evil influence of wicked people],