Rashi: It is what Hashem gave to Moshe written, and also orally.

R. Yonah #1: One's father and mother desire his good conduct and Musar. This Sefer constantly warns a son to hear his father's Musar. The father is commanded to rebuke him, for a youth's Sechel is not complete until he matures, and "Yetzer Lev ha'Adam Ra mi'Ne'urav" (Bereishis 8:21). He conducts according to his desire. His Sechel does not help him to rebuke his Nefesh and abandon the ways of his desire. If he will accustom himself to follow his desire in youth, the power of desire in him will be strengthened. When he will mature and his Sechel will be complete, and he will want to separate from the ways of his desire, it will be difficult due to his upbringing and habit. Therefore, his parents must help him with their Sechel, and rebuke him and guide him in a straight path in his youth - "Gam Ki Yazkin Lo Yasur Mimenu" (22:6). The way of rebuke is "Chanoch l'Na'ar Al Pi Darko" (ibid.) Chazal said that the Yetzer ha'Ra is in a person 13 years before the Yetzer Tov (Avos d'R. Nasan 16:2).

R. Yonah #2: It is Torah; Hashem is "[ha'Lo Hu] Avicha Kanecha" (Devarim 32:6}, "Atah Hashem Avinu" (Yeshayah 63:16).

Malbim: These are the foundations of the laws of Chachmah. The first Musar, that a man rebukes his son, is something that one cannot cast any doubt in it. Refer to 1:10:2:3.

Rashi: The Torah of your Umah (nation), Keneses Yisrael ¹ . This is like "Mah Imecha Leviyah" (Yechezkel 19:2). They are Chachamim's words; they added new laws, and made fences for the Torah.

R. Yonah: It is Musar of your mother. Refer to 1:8:1:2.

R. Yonah (8): It is the enactments of the Avos, and Chachamim's fences for Torah.

Malbim: It is the Torah that your mother teaches to you.