It’s said in this parsha, Parshas Shemini, that Hashem Himself sent down a fire to burn on the Mizbeach (Altar), which had to be maintained by the Kohanim. We also have this week the incident of Nadav and Avihu, in which they brought a foreign fire to the Mizbeach which lead to their souls being incinerated (according to Midrash Tanchuma). There are various mitzvos brought in regards to kashrus and the ideas of tumah and taharah, impurity and purity.
Practically speaking, when it comes to avodas Hashem, there are several things we can learn, both in p’shat and halocho, and in terms of the more psychological and less physical parts of these services. The fire from Shomayim is a hint towards the initial inspiration that a person feels in regards to serving Hashem: it literally comes down from Heaven and, the persons mode of service, shown through the Mizbeach, becomes illuminated and full of enthusiasm. To sustain this process, a person must learn Torah, as shown through the description of the service of the Kohanim who would bring wood every day. The wood is a remez (hint) to the Torah, as the Torah is referred to as the Etz Chaim, the Tree of Life, hence the enthusiasm of a person and their sincerity in serving Hashem is maintained through sustaining this fire through learning Torah. The inyan of Nadav and Avihu is also interesting, and there’s much to learn from there.
A frailichen lechtigen Shabbos, we should be zoche to maintain the same levels of feeling simcha and freedom we had on Pesach throughout the whole year!