Rabbi Moshe Ben-Chaim
"Whomever occupies himself with the Torah for its own sake, merits many things; not only that but he gives worth to the whole world. He is called a beloved friend; one that loves God; one that loves humankind; one that gladdens God; one that gladdens humankind. And the Torah clothes him in humility and reverence, and prepares him to be a tzaddik..." (Avos 6:1)
Note that he is only "prepared" to become a tzaddik (righteous person). Why is he not "immediately" a tzaddik, as he is immediately “clothed in humility and reverence?”
This is because a tzaddik is not defined by individual, discreet acts. He does not achieve the status in a mere moment. A tzaddik is not one who perfected himself in a singular area. A tzaddik is one who is perfect in all aspects of his personality, and perfect in all his relations, as Rashi says (Avos 6:1) "He walks perfectly." God too uses the same language telling Abraham, "Walk before Me and be perfect" (Gen. 17:1). "Walking" in a certain path (philosophy) refers not to an individual action, but to an ongoing lifestyle. Therefore, Pirkei Avos says that one who learns with no ulterior motive, has the proper preparation in order to become a tzaddik, but he is not a tzaddik yet. A tzaddik earns that title only after expressed perfection in every aspect of his personality and lifestyle, which can only be achieved over much time.