But even without that place in Deuteronomy, it is implicit in the entire book of Deuteronomy. There is a constant emphasis that keeping the laws of the Torah are the life and the good. And not keeping the laws of the Torah are death and evil.
The thing that makes this difficult is the teachers of Torah tend on the whole to be demons. I am not really sure why this is, but it has been obvious to me for a long time. Even from the very beginning of my learning Torah intensely, I was quite aware of this problem. But I was certainly the only one. Everyone else in yeshiva thought the supposed teachers of Torah outside of the yeshiva world were perfectly fine people. I had no idea why people were not able (or not willing) to see the difference between the roshei yeshiva [teachers of Torah in authentic Litvak yeshivas] that are sincerely devoted to the holy Torah, and the supposed teachers of Torah outside the yeshiva who are satanic demons as a rule. [I have never seen an exception to this rule.]
Even in Torah literature you find this willful ignorance.
In any case, the simple way to make the distinction is plain and simple. People connected with an authentic Lithuanian yeshiva are in general very good. But in the religious world--the minute you walk outside the door of the authentic yeshivas, one encounters the Sitra Achra [unclean and unholy Dark Side] immediately.