EXOD517 A teacher must make sure that his students understand what he teaches them. The Mechilta cited by Rashi states that this is what the Almighty told Moshe: "it should not enter into your mind to say, ' I will teach them the laws two or three times until they know them, but I won't try myself to make them understand the reasons for the laws and their explanations.' The Torah therefore states, 'Which you shall set before them,' as a set table which is ready for a person to eat from." Rabbi Yisroel Yaakov Lubchanski said that from here or we learn how we are obligated to teach others. It is not sufficient to merely repeat a lesson two or three times. Rather, a teacher must relate the ideas to the student with their complete explanation. There are several reasons why a teacher might hesitate to delve into the explanations behind the laws. He might lack the patience to explain the matter properly; or he might prefer to spend his time increasing his own knowledge and therefore does not want to spend time explaining everything thoroughly; or perhaps he might be afraid that if he tells the students everything he knows, he will no longer be considered their teacher, since they will be his equals in knowledge. But, said Rav Yisroel Yaakov, we see from God's command to Moshe that: 1) A teacher must acquire the patience necessary to explain matters at length. 2) Although Moshe would have been able to attain greater heights if he would have devoted all his time to his own spiritual elevation, God commanded him to use his precious time to explain the laws to the people. 3) A teacher must have his students' best interest in mind, rather than his own. (Ohr Hamussar, vol. 1, pp. 56-60).