Seeing you have purified your souls in your obedience to the truth through the Spirit in sincere brotherly affection, love one another from the heart fervently:
"Heart" (kardia) refers to "things done from the heart i.e. cordially or sincerely, truly (without simulation or pretence)" (Thayer 3325-1-2588). Sincere, pure love is to rise from an clean heart unceasingly. Love should rise out of our hearts as water does from a natural spring that rises out of the earth unceasingly. We are to love one another "fervently" (ektenos), "earnestly, fervently" (Thayer 200-1-1619). 