Love is a Maiden's Strength「愛は乙女の力 Ai wa Otome no Chikara」 is the 229th chapter of the manga, Nanatsu no Taizai.
Q235. Eight-san: Is there a Goddess inside of Solaseed's lute?
Nakaba: Well spotted! Exactly right! But as far as what kind of goddess is inside, that's a mystery.