What is the meaning of "Tzedakah Titzor Tam Darech"?
R. Yonah: The merit [of his Tzedakah] will guard him from sin. We learn from the end of the verse.
Malbim: Tam Darech is one who path is pure via nature. He does not lean to desire. Nothing is lacking in his path; lack and sin are the opposite of Temimus. Evil will not make him crooked, for his path is pure via nature, and he fixes his path via intellectual etiquette, to do Tzedek and Mishpat, like Sechel obligates, and to despise evil. Even so, if he does not go in Tzedakah (Mitzvos Bein Adam la'Makom), which etiquette does not obligate, he will veer from Temimus, for he does not know the correct path. Sechel cannot judge everything, what is good and what is evil. Only Tzedakah will guard a Tam Darech. Also Tzedakah without Tam Darech could stumble, for he might do Tzedakah for other motives, and when he will find benefit in the opposite, he will veer [from Tzedakah].
What is the meaning of "v'Rish'ah Tesalef Chatas"?
Rashi: Chatas is like Chotei. Since he is a total Rasha, the verse calls it Chatas. A sinner, his evil ruins and lowers him. Siluf is always ruining and making stumble - "Iveles Adam Tesalef Darko" (19:3), and evil will come upon him.
R. Yonah: An Aveirah leads to an Aveirah; the 'reward' of a sin is another sin (Avos 4:2). Tesalef is to make the one who did it crooked, until it will bring him to sin.
Malbim: One who has Chatas, i.e. a shortcoming that he leans towards desires - this is the concept of Chet, which is due to desire - evil will rule over him to make his way crooked.
