"Ask your father and he will relate it to you, your elders and they will tell you." (32;7)
Rashi (32;7) states that the "your father" refers to the prophets and that "your elders" refers to the Sages.
However, what exactly is the difference between the prophets and the Sages that a father is compared to a prophet and a grandfather (elder) is compared to a Sage?
Rabbi Yochanan Zweig explains that a prophet is required to order the people to follow Hashem's commandments whereas a Sage is merely obligated to restate the commandments to the people. Similarly, when a child does something wrong their father is obligated to order him to fix his ways while a grandfather is merely required to tell the child how he should act.
We could now also explain why the pasuk states "he will relate it to you" by a father and "they will tell you" by a grandfather. Rabbi Zweig explains that "he will relate it to you" implies an obligation to teach one to follow Hashem's commandments whereas "they will tell you" implies an obligation to merely inform others of how they should act.