Musar על נדרים 123:11

He who is truly a servant of G-d, will not be satisfied with serving Him minimally. He will not be content to take silver mixed with dross and lead, that is, divine service mixed with impure motivations, but rather only with the clean and pure as is befitting. Then he will be called "one who does a mitzva as it is stated", of which our sages of blessed memory said: "whoever does a mitzva as it is stated, will receive no evil tidings" (Shab.63a). Likewise they said: "do [good] deeds for the sake of their Maker, and speak of them for their own sake" (Nedarim 62a).