10 Attend closely to the catechisings, and though we should prolong our discourse, let not your mind be wearied out. For you are receiving armour against the adverse power, armour against heresies, against Jews, and Samaritans, and Gentiles. You have many enemies; take to you many darts, for you have many to hurl them at: and you have need to learn how to strike down the Greek, how to contend against heretic, against Jew and Samaritan. And the armour is ready, and most ready the sword of the Spirit: but thou also must stretch forth your right hand with good resolution, that you may war the Lord's warfare, and overcome adverse powers, and become invincible against every heretical attempt.
Source: Catechetical Lectures (New Advent)