In this aliyah, the Torah continues with the halachos of the Levi'im, specifically addressing a Levi who comes from his city to serve in the Beis HaMikdash. The Torah establishes his right to serve and receive an equal share in the avodah and the menachos, even when it is not his designated mishmar (shift). This section ensures that every Levi has a portion in the holy service when he comes to the place that Hashem chooses.
The aliyah then transitions to a strict warning for Bnei Yisrael as they prepare to enter Eretz Yisrael, forbidding them from learning or imitating the abominable practices of the Chana'anim. The Torah explicitly prohibits passing one's children through fire for Molech, as well as various forms of sorcery, divination, consulting ghosts, and inquiring of the dead. We are commanded to distance ourselves entirely from these dark practices, which are the very reason Hashem is driving these nations out, and instead we are given the positive mitzvah to be tamim—wholehearted and simple in our emunah—with Hashem.
The Torah is telling us in this Aliyah that when a Levi wants to serve in the Beis HaMikdash, he can come and do so "b'chol avas nafsho", with all the desire of his soul. Right after this, the Torah warns us not to turn to sorcerers, diviners, or those who inquire of the dead, and concludes with the famous yesod: "Tamim tihyeh im Hashem Elokecha", you must be wholehearted and simple with Hashem.
Lichoira, what is the connection between the Levi's burning desire to serve and the prohibition against seeking out fortune-tellers and sorcerers? The Tanna is teaching us a deep sevara about how a Yid is meant to live. The goyim are always looking for shortcuts, predictions, and magical ways to control their future because they lack a real, living connection to the Borei Olam. But a Yid doesn't need to look into the future or try to force things through external means. When you have that inner "avas nafsho", that deep, simple desire to just be close to Hashem and do His ratzon, you don't worry about what tomorrow brings. You are completely tamim, whole and at peace, knowing you are in Hashem's hands.
This is our daily avodah. The yetzer hara constantly tries to make us anxious about the future, making us feel like we have to control every outcome or find some quick fix to our worries. The teretz to this anxiety is "Tamim tihyeh." When we focus our energy on simply wanting to do the ratzon Hashem right now, in this very moment, all that worry melts away. We don't need to know the future when we know Who is running the future.
Today, when you feel anxious about how a certain situation will turn out, catch yourself, let go of the need to control the outcome, and say to Hashem: "I don't need to know what tomorrow brings; I only want to do Your ratzon simply and wholeheartedly today."