Firstly, it suggests that actions speak louder than words. The speaker is advising treating their partner with such love and care that the verbal expression of love becomes almost unnecessary because it is so clearly demonstrated through actions.
Secondly, the response, "I know you do," signifies a strong sense of trust and confidence in the love being shared. It implies that the love is so consistently and sincerely shown that there is no need for constant verbal reassurance.
In essence, this statement encourages a love that is profound and unwavering, where the actions and behaviors within the relationship consistently reflect the depth of affection, creating a bond where both partners feel deeply loved and secure.