Here "heart" is a metonym for a person's emotions. This idiom expresses strong affection. AT: "I love you very much" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-idiom]])
The abstract noun "compassion" can be translated with the verb "love." AT: "and I love you as Christ Jesus dearly loves us all" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])