The Meor Einayim (Likutim כשרצה ה"ד) writes, "All salvations can be found in the Torah... For example, if someone needs food, his salvation is concealed in parashas hamon. Whoever needs parnassah should read parashas hamon daily, and he will be zoche to chesed from parashas hamon. Similarly, all other matters are in their place, in the Torah."
Every Shabbos, for twenty-two years, Rebbe Menachem Mendel of Riminov zt'l would teach lessons from parashas hamon to bring parnassah for Bnei Yisrael.
It is also repeated in the name of Rebbe Menachem Mendel of Riminov zt'l that reading parashas hamon on Tuesday of parashas Beshalach is mesugal for parnassah.
The Chidushei HaRim writes in a letter: "Rosh Chodesh Nisan, 5612: I thought of an idea that I should make a chiddush in parashas hamon each day, and thereby my parnassah will come from the Torah. As the Midrash (Bereishis Rabba 97:3) states, יום בכל פרנסה, every day has its parnassah..."
Shulchan Aruch (Orach Chaim 1:5) states, טוב המן פרשת ...לאמר, "It is good to say...parashas hamon." The Mishnah Berurah writes, "The Yerushalmi says that whoever says parashas hamon daily is guaranteed that he won't ever lack parnassah."
The Tashbatz quotes this Yerushalmi and adds ערב ואני, "I guarantee it."
When one says parashas haman, he strengthens his belief that Hashem gives him parnassah, and this emunah is mesugal for attaining parnassah.
לגלגלת עומר (16:16) can be translated that the parnassah comes לגלגלת from the emunah that is in a person's mind.
It states (Yirmiyahu 7:28) ונכרתה האמונה אבדה מפיהם, meaning Hashem is complaining that the nation lost their emunah (האמונה אבדה). They don't even speak about emunah (מפיהם ונכרתה).
The Beis Avraham says that the pasuk is hinting, האמונה אבדה, if you lost your emunah, מפיהם ונכרתה, food isn't in your mouth. A person might lack parnassah and food, chalilah, because he lacks emunah. This is because emunah is mesugal for attaining parnassah.
Why is there a custom to give birds food on Shabbos Shirah? The Yismach Yisrael explains that when you feed an animal, like your cow or your horse, it feels that it deserves the food. The animal worked for you, so he deserves to be fed. But birds don't do anything. When they are fed, they understand that this is an underserved gift. We, too, seek to attain the awareness that Hashem doesn't owe us anything, and if we have food, we should thank Hashem for His chesed.
Furthermore, we can explain that birds raise their heads when they drink. They bend, drink some water, and then lift their heads again. This signifies how we should be when it comes to parnassah. We do
