Rashi on TanakhPsalms 15

and speaks truth in his heart The good that he says in his heart is true. He is not a hypocrite [lit. one in mouth and one in heart].

He did not slander with his tongue Ankuza in Old French, to accuse, as (in II Sam. 19:28) “And he slandered (וירגל) your servant.” This psalm is to inform us of the [proper] measure of piety.

neither did he take up reproach Rapporta in Old French, to report.

upon his kinsman If his kinsman committed a transgression for which he was punishable, he would punish him with justice, and he did not bear upon himself his reproach, that the reproacher should have an excuse to say, “So-and-so, your relative, committed such-and-such a sin, and you covered up for him.”

A base person is despised in his eyes One who is base with his wickedness is despised in the eyes of the righteous man, e.g. Hezekiah, who dragged his father’s remains in disgrace.

he swears to hurt himself.

and does not retract his oath. How much more does he not retract it if it concerns something that is not to his hurt!

nor did he accept a bribe, etc. against a poor man, to condemn him in judgment by judging perversely. Our Sages explained it further to mean that he would not accept a bribe to exonerate him in judgment, and he certainly will not take a bribe to pervert the judgment.

shall not falter and he deserves to sojourn in Your tent.

shall not falter forever If he falters, his faltering will not be permanent faltering, but he will falter and ascend.