You say that a true faith can not be without the fruits of love. Why not?

Luther:

Would you not go mad with joy if you truly believed what God promises you? Would you not love God fully because He wants to give such a great affluence to someone who has done nothing to earn it? Therefore, behind faith a wonderful feeling of sweetness follows completely in your heart, that makes your spirit magnanimous and fruitful. That is the love given by the Holy Spirit in the faith in Christ. That love pulls you to Christ, the munificent and good Testator. And because of that you become a new and different person.