The first aliyah begins with G-d commanding Moshe to admonish the Jewish people to be holy, then summarizing several laws such as: fearing parents, observing Shabbos, leaving over parts of the harvested field for the poor, not to lie, not to put a stumbling block before the blind, and others. Not putting a stumbling block before the blind refers to matters such as causing others to sin, or misleading the ignorant, such as saying that something is kosher when it isn't.