The Epistle to the Hebrews, the authorship of which has been long debated, urges the Hebrew Christian community not to fall back into Judaism.

Hebrews 4

4:12 For the word of God is quick, and powerful, and sharper than any two-edged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart.