신명기 4:3 해설: Chizkuni, Ramban, Ibn Ezra & Sforno

עיניכם הרואות, “Your eyes which have seen, etc.;” in verse 1 of this chapter Moses had told us to observe the laws of the Torah to ensure that the people whom he addressed would indeed inherit the Holy Land. It was also a warning not to once more miss that opportunity as it had been missed a few months earlier by 24000 of them who had worshipped the Peor. This had happened to them although up until that moment their conduct had entitled them to inherit their shares of that land. The previous generation had all died because of the sin related to the spies, and immediately after that G-d had told me that the time had come to make up for this now, and even now some of the people had wasted that opportunity by worshipping Peor, The time had therefore come to repeat the warning not to deviate by one iota in the laws concerning idolatry.

YOUR EYES HAVE SEEN. Now Moses comes to forewarn on the details of the commandments, and he begins with [the prohibition against] idolatry which is the root of all [the commandments].

There is no need for witnesses to substantiate the warning “so that you may live” [: 1], because You have seen with your own eyes what happened with Baal Por (i.e., because of Baal Por — as in many other Hebrew words): Everyone who did not worship Baal Por is now alive.