R. Yonah: It says "v'Orach Yesharim Selulah" (15:19). One whose nature is straight, he yearns for straightness and recognizes the straight. His nature helps him to rule over his Ru'ach. The verse informs that first Yesharim strive to veer from evil and be careful from any sin. First, one must contemplate all his ways and fix his Midos and distance them from sin. There will not be found in his hand or Nefesh gleanings of sin, or matters that cause sin or lead to stumbling. First one must be careful not to distance from the Creator, not via sins or Midos that lead to sins and are hateful to Hashem. Afterwards, he puts to his heart to gather 'harvest' of good deeds and to straighten others' ways, to learn and to teach. He learns deeds and to come close to Hashem in love and fear of Him. Mesilah is a paved path. It is straight, and stumbling blocks were removed. From it, one reaches his destination - "v'Haysah Mesilah" (Yeshayah 11:16). Via Sur me'Ra, Yesharim reach Yir'as Hashem and love of Him, and the attribute of serving Him the entire day. From being careful they will come to Zerizus.

Malbim: A Yashar's nature leans towards straightness. Unlike a Tzadik, he has no inner war in his Ru'ach. He has a paved path without stumbling blocks or impediments. He veers from evil, for his path is clear from desires and Yetzarim of the heart - "v'Orach Yesharim Selulah" (15:19).

R. Yonah: The foundation of the level of Yesharim is Sur me'Ra. This is their initial effort. Even though their nature helps them, and they are close to veering from evil and conquering their Yetzer, every person can guard his way and veer from evil. Anyone who wants to guard his Nefesh, he should guard his way and conquer his Yetzer. The verse is put next to Chachmah, for Yesharim first strive for fear of sin, before they strive for Chachmah. They make it a path for all attributes - anyone whose fear of sin precedes his Chachmah, his Chachmah lasts. (Avos 3:12). Fixing the Nefesh is via fixing Midos. When the Nefesh removes the garment of desire for pleasures, so it will not overpower to make the person stumble in sin, it is guarded from sins and from distancing from the Creator. After it is saved from distancing, it can draw close via honored deeds and Kadosh Avodah.

Malbim: One who does not have a paved path, and he needs to go on a path that is not paved, he is in danger. Many fight against him to tilt him off the path, and kill his Nefesh. One who guards his Nefesh guards his path exceedingly, lest he fall in one of the traps, or lest he lean to crooked minor paths, and fall prey to Yetzarim of the heart, bad Midos and those who ambush his Nefesh.