Permanent poles and constant candles
בטבעת הארן יהיו הבדים לא יסרו ממנו
The poles shall remain in the rings of the Aron; they shall not be removed from it
The Mishkan, also known as the Tabernacle, was the Jews’ portable Temple in the wilderness. When they encamped, they would construct it according to the Divine architecture given over by Moshe. When they would travel, they would pack everything up. Many of the vessels in this portable Temple had poles to allow easy transportation. Designated families of the Leviim would be tasked with carrying these vessels on their shoulders via these poles.
Unique among the Mishkan’s vessels, the Aron Kodesh, the Holy Ark, containing the Ten Commandments, had poles which were never to be removed. Their removal would constitute a transgression of one of the mitzvos of the Torah. The Temple Altar, and the Shulchan, for example, while they also had poles, had no such prohibition. They would be inserted during travel and removed upon encampment. What made the Aron Kodesh so special that its poles carried with them this prohibition, that they should never be removed?
The Menorah in the Temple had a special mitzvah. Twice daily, once in the morning, and once in the evening, the oil and wicks of the Menorah were to be arranged. Included in this mitzvah was to also light the Menorah. What comes out then is that in the middle of the day, in broad daylight, the Menorah was lit. Clearly, its light wasn’t necessary. In fact, our Sages say that the Menorah’s light was never needed, for does G-d need light to see? In order to drive this point home, not only was there a mitzvah to light it at night, but to also light it by day. Since it’s obvious that the light provided in the day wasn’t necessary, it became clear that even the light provided at night wasn’t necessary.
We can say a similar idea with the Aron Kodesh. We are taught that the Aron Kodesh would miraculously support itself upon its supporters. Meaning, although people were “carrying it”, it in fact was carrying itself. That means its poles weren’t really necessary, unlike the poles of the other vessels. To demonstrate this fact, all other vessels could have their poles removed. Not so the Aron Kodesh. Its poles were to remain there, even when the Jews weren’t traveling. This was to show that the poles were there for some other purpose, but not for carrying it. The Aron Kodesh didn’t need to be carried.
 Based on Meshech Chochmah to Exodus 25:15
 Exodus loc. cit.
 Ibid 27:7
 Ibid 25:8
 Mishneh Torah Hilchos Temidin UMussafin 3:10
 Exodus 27:21; Sefer HaMitzvos Aseh § 25; Sefer HaChinuch § 98. This is what the gemarra calls הטבת הנרות (Yoma 14b)
 This is the Rambam’s opinion in Sefer HaMitzvos loc. cit., Mishneh Torah loc. cit. § 12, and in his commentary to Tamid 3:9. Not being familiar with the sugya, I’d say that the Rambam’s opinion makes logical sense. If the mitzvah was to merely arrange the oil and wicks, what’s the point of doing it twice a day? If the Menorah was only lit once, then one of these arrangements of oil and wicks will be wastedW
 Shabbos 22b
 Sotah 35a