(כב) וַיַּסַּע מֹשֶׁה אֶת יִשְׂרָאֵל מִיַּם סוּף וַיֵּצְאוּ אֶל מִדְבַּר שׁוּר וַיֵּלְכוּ שְׁלֹשֶׁת יָמִים בַּמִּדְבָּר וְלֹא מָצְאוּ מָיִם. (כג) וַיָּבֹאוּ מָרָתָה וְלֹא יָכְלוּ לִשְׁתֹּת מַיִם מִמָּרָה כִּי מָרִים הֵם עַל כֵּן קָרָא שְׁמָהּ מָרָה. (כד) וַיִּלֹּנוּ הָעָם עַל מֹשֶׁה לֵּאמֹר מַה נִּשְׁתֶּה. (כה) וַיִּצְעַק אֶל יְהוָה וַיּוֹרֵהוּ יְהוָה עֵץ וַיַּשְׁלֵךְ אֶל הַמַּיִם וַיִּמְתְּקוּ הַמָּיִם שָׁם שָׂם לוֹ חֹק וּמִשְׁפָּט וְשָׁם נִסָּהוּ.
(22) And Moses led Israel onward from the Red Sea, and they went out into the wilderness of Shur; and they went three days in the wilderness, and found no water. (23) And when they came to Marah, they could not drink of the waters of Marah, for they were bitter. Therefore the name of it was called Marah. (24) And the people murmured against Moses, saying: ‘What shall we drink?’ (25) And he cried unto the LORD; and the LORD showed him a tree, and he cast it into the waters, and the waters were made sweet. There He made for them a statute and an ordinance, and there He proved them;
This happened right after the parting/ crossing of the Red Sea. All of the Jewish people thought that they were trapped and that they were going to be killed. They were being pessimists and had no faith in God or Moses.
(יז) וַיְהִי בְּשַׁלַּח פַּרְעֹה אֶת הָעָם וְלֹא נָחָם אֱלֹהִים דֶּרֶךְ אֶרֶץ פְּלִשְׁתִּים כִּי קָרוֹב הוּא כִּי אָמַר אֱלֹהִים פֶּן יִנָּחֵם הָעָם בִּרְאֹתָם מִלְחָמָה וְשָׁבוּ מִצְרָיְמָה. (יח) וַיַּסֵּב אֱלֹהִים אֶת הָעָם דֶּרֶךְ הַמִּדְבָּר יַם סוּף וַחֲמֻשִׁים עָלוּ בְנֵי יִשְׂרָאֵל מֵאֶרֶץ מִצְרָיִם.
(17) And it came to pass, when Pharaoh had let the people go, that God led them not by the way of the land of the Philistines, although that was near; for God said: 'Lest the people regret when they see war, and they return to Egypt.’ (18) But God led the people about, by the way of the wilderness by the Red Sea; and the children of Israel went up armed out of the land of Egypt.
The people of Israel still believe that Egypt is a protective environment and a place they can turn back to. They need to feel protected, so God needs to show them that he is capable of providing this for them. Maybe these Jews were just meant to be slaves forever?
When Ibn Ezra asks why the Israelites didn't fight back to the Egyptians, he says, "The Egyptians were masters to the Israelites. exodus generation was accustomed from the youngest age to suffer under the yoke of Egyptian oppression. Their spirit was broken. How could they stand up and fight their masters... after all they were inexperienced in the art of war..."
(יח) עֵץ חַיִּים הִיא לַמַּחֲזִיקִים בָּהּ וְתֹמְכֶיהָ מְאֻשָּׁר.
(18) She is a tree of life to them that lay hold upon her, And happy is every one that holdest her fast.
God thought that by giving the Jewish people the Torah, it would give the Jews faith in God. This did not work because the Jews created the Golden Calf.