to go straight ahead on a path, or to lead and direct others along one
This is the concrete, physical side of the word: moving forward on a road, and by extension steering people onto the right course. The book of Proverbs uses it for the moral image of a journey. A person can walk on in the way of understanding or refuse to advance down the path of the wicked, and a teacher can direct a student's heart along the good road.
The prophet Isaiah sharpens the same idea into a charge against Israel's rulers. The very leaders who were supposed to keep the nation walking straight are the ones sending it astray, a bitter play on the word that pairs guiding with misleading in a single breath. From there the sense stretches to putting something back in order: setting a wrong situation right.
English has no one word for this. Translators reach for walk, advance, lead, guide, direct, and set right depending on the verse, because the picture underneath them all is forward motion on a straight track, either taken oneself or imposed on someone else.
Nuances
Whether Isaiah 1:17 commands setting the oppressor right or relieving the oppressed, which turns on whether the following noun is read as the active wrongdoer or the passive victim.
- majoritySet the oppressor straight; the command corrects the wrongdoer, fitting the surrounding calls to Israel's judges and rulers.; H. Wildberger, Isaiah 1-12 (Continental Commentary); J. Blenkinsopp, Isaiah 1-39 (Anchor Bible 19); J. J. M. Roberts, First Isaiah (Hermeneia)
- minorityRelieve the oppressed; the command helps the victim, reading the noun as a passive participle.; Septuagint, Isa 1:17 (rhysasthe adikoumenon); Vulgate, Isa 1:17 (subvenite oppresso)