2 verses have
sincere
in Edition Clear Qur'an by Talal Itani / Az-Zumar (The Groups)

39:3Is not to God that sincere faith is due? As for those who take guardians besides Him, “We only worship them that they may bring us nearer to God.” God will judge between them regarding their differences. God does not guide the lying blasphemer.

39:14Say, “It is God I worship, sincere in my faith in Him.”