The heart is a metonym for what the person thinks and loves. Tearing one's clothes is an outward act of shame or repentance. Alternate translation: "Change your way of thinking; do not just tear your garments" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The abstract noun "faithfulness" can be stated as "faithful" or "faithfully." Alternate translation: "always faithful to his covenant" or "always loves faithfully" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])