The core prohibition is rooted in the pasuk 'לפני עור לא תתן מכשול' — do not place a stumbling block before the blind (Vayikra 19:14) — which the Gemara in Avodah Zarah 6b reads as forbidding one from facilitating another's transgression even where the other could in theory sin on his own, and which Moed Katan 17a applies even to striking one's grown son, since this is likely to provoke the son to strike back and sin gravely himself.
The Rishonim extend this verse well beyond literal physical obstacles to any act of enabling or luring another into wrongdoing: the Mishneh Torah (Theft 5:1) forbids buying from a thief because doing so 'strengthens the hands of transgressors' and causes him to steal again, the Mishneh Torah (Robbery and Lost Property 5:1) forbids assisting a robber to legitimize stolen goods on the same grounds, and Sefer HaChinukh 232 generalizes the lo taaseh to include giving a fellow bad advice or helping a transgressor, citing the Sifra's example of telling someone to sell his field only in order to seize it from him.
A parallel set of sources forbids deceiving or manipulating people through speech and conduct even absent formal sin: Shulchan Arukh, Choshen Mishpat 228:1-6 and the Mishneh Torah (Sales 18:1) forbid deceiving people in words and 'stealing the mind' (geneivat da'at) of others, the Mishneh Torah (Human Dispositions 2:6) forbids flattery, duplicity, and any word of deception, and Chullin 94a states in the name of Shmuel that it is forbidden to deceive people, even a non-Jew, giving the example of creating a false impression through a seemingly generous gift.
The theme of verbal mistreatment (ona'at devarim) reinforces that halacha guards against psychological harm, not only physical or financial harm: Bava Metzia 58b and its parallel in Shulchan Arukh, Choshen Mishpat 232:1-2 and Sefer HaChinukh 338 catalogue forms of hurtful or manipulative speech, such as reminding a penitent of his past or a convert of his ancestry, and Bava Metzia 59a stresses that this applies especially 'with one who is with you in Torah and mitzvot' and particularly toward one's wife.
Beyond withholding help from a scheme against another, the sources require active disclosure: the Mishneh Torah (Murderer and the Preservation of Life 1:14) and Shulchan Arukh, Choshen Mishpat 426:1 obligate a person who hears that others are plotting harm or 'laying a trap' for his fellow to inform him, on pain of violating 'do not stand idly by the blood of your fellow,' and the Chafetz Chaim (Principle 9:1-2) similarly requires warning a friend who is about to enter a harmful partnership, provided the warning is given for a pure purpose and without exaggeration.
Other sources sharpen the deliberateness element: Shemot 21:14 singles out one who schemes 'בעורמה' (with cunning) against another to kill him for the harshest treatment, and Sotah 21b defines the 'clever wicked person' as one who manipulates a judge or structures a gift specifically to disqualify a poor man from charity he would otherwise receive — both cases turning on calculated deception designed to produce an unjust result.
Later authorities continue applying this framework to concrete cases of luring or misleading others: Igros Moshe CM 2:28 holds that misrepresenting facts such as the number of students is forbidden as theft, as geneivat da'at, and as a desecration of God's name, with no justification permitted, and Sha'arei Teshuvah 3:184 treats one who misleads a fellow into believing a favor was done for him, when none was, as graver than theft because of the gravity of false speech.
Maayan Omer (12:2:1) addresses such conduct as forbidden, illustrating it with the case of offering someone food that is prohibited for him to eat, and raises the further question of whether one may eat it oneself merely to avoid causing him offense.
Revavos Ephraim (3:527) holds that it is forbidden to perform an act that causes another person — or even a non-Jew — to transgress a prohibition, and on that basis forbids lending money without witnesses even where the borrower is not expected to deny the debt, since this could still lead him to deny it.
Tzitz Eliezer (15:12) addresses misleading people and distancing oneself from falsehood, covering deception in medical publications, falsehood in writing, falsehood that causes no harm but yields personal benefit, and the prohibition against deceiving non-Jews.
Igros Moshe (OC 5:13) distinguishes between causing another physical harm, which falls under obligations between people, and causing another to sin, which falls under obligations between a person and God, and maintains that one may not place an obstacle of sin in the world regardless of which category applies.