mitzvos and middos

Question

i heard the idea that mitzvos are to improves character what is/are the source/s for this?
do others argue?

what i found is in the name of the Ramban
here and here
but were it the original Ramban? are there other Jewish sources claiming this?

Answer 1

As kouty pointed out in the comments, you can find the Rambam in his introduction the Avot, known as The 8 chapters, in chapter 4 where he discusses at length how the Torah and Mitzvoth perfect one's character, when done properly.

Here's a snippet:

וזאת התורה התמימה המשלמת אותנו כמו שהעיד עליה יודעה‏

The perfect Law which leads us to perfection as one who knew it well testifies

Others that mention this concept are the Chinuch in Mitzva 16 for example. There he writes:

ועתה בני, אם בינה שמעה זאת, והטה אזנך ושמע (משלי כב יז), אלמדך להועיל בתורה ובמצות. דע, כי האדם נפעל כפי פעלותיו, ולבו וכל מחשבתיו תמיד אחר מעשיו שהוא עוסק בהם אם טוב ואם רע, ואפילו רשע גמור בלבבו וכל יצר מחשבות לבו רק רע כל היום, אם יערה רוחו וישים השתדלותו ועסקו בהתמדה בתורה ובמצות, ואפילו שלא לשם שמים, מיד ינטה אל הטוב, ומתוך שלא לשמה בא לשמה, ובכח מעשיו ימית היצר הרע, כי אחרי הפעלות נמשכים הלבבות. ‏

And now, my son, 'If you have understanding,' 'incline your ear and hear,' and I will teach you to benefit from Torah and the commandments: You must know, that a man is acted upon according to his actions; and his heart and all his thoughts always follow after the actions that he does - whether good or bad. And even he who in his heart is a complete sinner and all the desires of his heart are only for evil; if his spirit shall be enlightened and he will put his efforts and actions to persist in Torah and commandments - even if not for the sake of Heaven - he shall immediately incline towards the good. And from that which is not for its own sake comes that which is for its own sake [as opposed to being for personal gain]; for the hearts are drawn after the actions.