Rashi #1 and Targum Yonasan: Hashem called upon heaven and earth because they exist forever. Consequently, should Yisrael sin and Hashem punishes them, they will be available to testify that Hashem warned them. ¹

Rashi #2: He called upon them because they are examples that we should follow - Hakadosh-Baruch-u said to Yisrael 'Look up to the heaven that I created to serve you! Did the sun ever fail to perform what it was created to do? Did it ever fail to rise in the east and shine upon the world? ² See the earth that I created to serve you! Did it ever fail to perform what it was created to do? Did you ever plant seeds and they did not grow? Did you ever plant wheat and the land produced barley? And if heaven and earth, which are not subject to reward and punishment if they do or don't do their job, perform their tasks faithfully, you, who receive reward if you deserve it, and punishment if you sin, should certainly follow their example!' ³

Ramban: In Va'eschanan He appointed them to testify that Yisrael had been warned that if they sinned, they would perish quickly, wheres here, He was calling them to testify that He had placed two paths in front of Yisrael - life and death, which are synonymous with Brachah and Kelalah and that He had advised them to choose life so that they and their children will live. ¹

Rashi: Hashem is giving us a sound piece of advice - like a man says to his friend (favorite son - Rashi in Tehilim, 16:5) 'Pick a nice portion of my inheritance!', as he points to a good-quality piece of land. ¹

Yerushalmi Kidushin, 1:7: This Pasuk is the source for the Mitzvah incumbent upon a father to teach his son a. a trade and b. how to swim - as implied by the end of the Pasuk "Lema'an Tichyeh Atah ve'Zar'acha". ²

Targum Yonasan: "ba'Chayim" means the way of life - Torah, and it is the way of life in this world - which earns a person life in the world to come (as the Torah goes on to elaborate in the next Pasuk).

Seforno: Refer to 30:15:2:2. To teach us to choose eternal life, and as the Pasuk goes on to explain, not for the aspect of reward, but, 'in order to live with one's children (in this world) - to love Hashem and listen to His Voice ,,, '.

Yerushalmi Kidushin, 1:7: Refer to 30:19:3:2. And it also implies that someone whose father did not teach him a trade or how to swim is obligated to teach himself.

Targum Yonasan: Refer to 30:19:3:3.

Rosh and Da'as Zekenim (both in 11:27): It can be compared to two paths, one which is initially full of thorns, but ultimately becomes clear. The other, which is initially clear, later becomes full of thorns. And a Zakein is sitting at the crossroads and advising people to take the former road, even though initially, the latter road appears preferable. Those who follow his advice begin with difficulty, but end smoothly; Whereas those who do not, end up suffering. Similarly, those who follow the freedom of their hearts and indulge in sin, earn a little satisfaction in this world, but end-up burning in Gehinom; whereas those who toil and engage in Torah and Mitzvos, merit to go to Gan Eden, a land that is eternally smooth and satisfying.