In chapter 16 verse 3 the Israelites complain: Would that we could die by the hand of the Lord in Egypt where we would sit by the stew pots eating bread to our fill, that you have taken us out into this desert to kill the congregation of the Lord by hunger.
God responds that He will rain down upon them bread from heaven, mannah.
The Talmud tells us that we can do things which will cause us to die before our appointed time. It brings two examples: walking by an unstable wall and climbing on a rickety ladder. These are dangerous actions. If you put your life in jeopardy you can't expect a miracle to save you. You might die before your time. These two examples are just that, examples. Any dangerous actions you take will take away God's watchful eyes. You are then left to face teh results of your beviour without divine providence.
With this insight we can understand the complaint of the Israelites on a theological level and not just a gastronomic one. Living in Egypt in the safety and material wealth of that civilization they were sure that if they died it was God's will. Putting themselves into risk by entering the desert without food they could no longer be sure that their deaths were not of their own doing. They could accept their own death if at least they knew it was the will of God. This explains the term "by the hand of God" in the above quoted verse. In Egypt they were sure their death was by the hand of God but in the desert they were unsure. Maybe it was by their own hand, because of their foolishness in following Moses.
God's answer to them is that for them the desert is not in the catagory of a dangerous place. Even here God was watching over them providing their essential needs: mannah and water. This reasured them that they were still under Divine Providence.
Compare order of asking for food and getting quailk and mannah with the order in devarim. Is this the same incodent?
Laws at Mara, shabbat, etc. How do we know we weere given laws then? Because of the Mannah. It says "Sham sam lahem chok umishmat." It says by the mannna not to leave ones place on shabbat. Verse 16:29 "Let no man leave his place on the seventh day."
Sefer Kuzari uses this to prove to Karaites that they need interpretation. This is idea that we need rabbinic law for understanding what is written but do we also need them to make gazerot? Also says hechinu asher heviyu , learn muktze from this. so same place teaches the need for both kinds of oral torah. and especially interesting because the location of these laws is before Matan Torah so therefore these laws have to be Oral teaching. Oral teaching which teach the need for an oral law.