Kedoshim: Chapter 15
"Nor put a stumbling block before the blind"

We are told that the title verse is referring to someone who curses a person behind their back; that evil speech ascends and prosecutes the speaker. Every word that people speak ascends and has a consequence. Also, one must not cause another to sin. Anyone who walks in the righteous path of Torah earns a share in the World to Come, since the words of Torah that he speaks ascend very high and are taken higher and higher. We learn the consequences for one who does not study the Torah in a pure way, and of someone who wants to learn Torah but cannot find a good teacher.