Rabbi Meir would say: Whoever studies Torah for Torah's sake alone, merits many things… and it [the Torah] prepares him to be righteous, pious, upright and faithful…
Our mishnah depicts an ascending dynamic from “righteous” to “faithful.” Every ascent to a new level builds upon the level below it and adds to it. Let us see how:
The tzaddik, righteous person, is an individual who performs all the commandments as per the letter of the law. All of his actions are in line with the Code of Jewish Law. He is righteous in thought, speech and action (the three garments of the soul, which are how the soul expresses itself in practice). Every person who engages in Torah study for its own sake is certainly a tzaddik, for study “for its own sake” is study for the purpose of putting the study into action.
The tzaddik does what has to be done, according to the letter of the law. This is a great quality, but it is the first rung of the ladder. From there, he has to keep climbing. After his external actions are rectified, he climbs to the level of a chassid, a pious individual, who goes above and beyond the letter of the law. To accomplish this, the chassid has to add a layer of emotions onto the layer of action that he has already mastered. When a person identifies emotionally with mitzvah performance, he wishes to fulfill more than the minimum requirement. The tzaddik is good, but one can always be better.
Above these two initial levels, the next level is described as being, “upright.” One who is described as “upright” is one who possesses a rectified frame of mind. To straighten one’s thinking, one has to learn enough Torah so that his thinking aligns and assimilates with the Torah’s way of looking at things.
The fourth level is described as being, “faithful.” Faithfulness is an attribute of Moses, about whom it is written, “In all my house, he is faithful.” True faithfulness is the binding of a covenant from a place of essential connection above and beyond reason. It comes from the highest level of the soul, the superconscious Crown, or keter, in Hebrew. The Hebrew word for “crown” (keter) shares a root with karat, ‘to cut,’ the Hebrew verb used for ‘cutting a covenant’). A covenant between two faithful lovers (and this is of course what should exist in the covenant of marriage) is “love that is not dependent upon anything.” This love endures even when one of the sides blemishes the conscious level of the relationship.
The upright person aligns his deeds with his great Torah wisdom, but a person who has the merit to be ‘faithful’ is completely aligned with Heaven, bringing light from Above to below.
 This does not refer to the consummate tzaddik of the Tanya, but rather, to a tzaddik who does not sin, but may wish to do so. In the terms of the Tanya, this person would be called an intermediate “beinoni.”
 Numbers 12:7.