Sifrei Devarim
(Devarim 12:28) "Take heed and hearken": If you take heed just a little, in the end you will hearken much. If you take heed of what you have heard, in the end you will take heed of what you have not heard. If you take heed of what you have now, in the end you will take heed of what you are destined to have.