The story of Uzzah happened.
Here’s a d’var Torah from Rabbi Yissochor Frand on the subject:
Calling Torah “Shira” Is Allowed; Calling It “Zimrah” Is Not Allowed
A pasuk [verse] at the beginning of Parshas Naso defines the varying duties of the different families of Levi. The job given to the family of Kehas was to carry the Aron HaKodesh [the holy Ark] on their shoulders during travel.
The Talmud [Sotah 35] discusses an incident in the book of Shmuel when King Dovid ordered that the Ark be transported by wagon. This was contrary to halacha. An incident occurred where the Aron almost fell off the wagon. Uzza reached up to try and save it from falling, and he was killed on the spot. The Talmud says that this punishment befell King Dovid because he referred to the words of Torah as ‘Zemiros’ (songs), as it is written “Your statutes were like songs (Zemiros) to me” [Tehillim 119:54]. (Rash”i explains that when Dovid was fleeing from King Shaul and was leading a tension-filled existence “on the run”, he was able to achieve ‘playful enjoyment’ in the words of Torah and they served to calm him down, like a soothing song.)
G-d responded, as it were, “About my Torah it says ‘If you blink your eye in it, you can lose it’ [Mishlei 23:5], and you refer to it as a song and plaything? I will cause you to err in a matter that even young school children are aware of — namely, the explicit verse [Bamidbar 7:9] that the Aron must only be carried on the shoulders of the family of Kehas (and not on wagons).” As a result of this ‘flippancy’ on King David’s part he forgot this halacha, and the unfortunate death of Uzza followed.
Rav Bergman, in his work “Shaarei Orah,” asks an obvious question: What is so wrong with referring to the Torah as “Sha-a-shuai”, a pleasant and uplifting thing (literally, a ‘play’ thing)? We are all familiar, with the verse “Lulei Torashcha Sha-a-shu-ai, az avadati b’anyi” [Tehillim 119:92] (If not for Your Torah which was my plaything, I would have been overwhelmed with my suffering). We do not find anywhere that Dovid is held accountable for this statement where he refers to Torah as a plaything.
The unavoidable conclusion is that Dovid’s crime in the earlier verse was not that he referred to Torah as a plaything (Sha-a-shu-ai), but that he referred to Torah as a song (Zemiros). But what is so terrible about calling Torah ‘Zemiros’? I would have better understood it, if the objection was that he called Torah a plaything. That might be objectionable. Torah is not Nintendo — it is not a game! Why is it a sin to call Torah ‘Zemiros’? Moreover, the Vilna Gaon makes the question stronger: the Torah itself refers to Torah as a Song: “And you write for yourselves this Shirah [Song]” [Devorim 31:19].
The Gaon answers that there exists a tremendous difference between “Zemirah” and “Shirah”. Zemirah, like the Zemiros of Shabbos, are finite. They have a beginning and end. [Kah Ribbon (a Sabbath song) starts with a Yud, it ends with a Lamed — and it’s over. All Zemiros are similar.] Shirah represents the infinite. Shirah represents the articulation and expression of feelings, which have no end and no beginning. When a person breaks out in Shirah, it is a manifestation of what his essence is all about. There is no end to that. It is not finite.
Torah can be called Shirah, but Torah can not be called Zimra. To refer to Torah as Zimra has the connotation that there can be a beginning to Torah and an end to Torah and then I would be finished with Torah. That is untrue. Torah can’t be finished. Torah is Shirah — the infinite expression of what a Jew is all about, his innermost essence. That was King Dovid’s sin.
Based on this distinction, the Ponevezher Rav (Rav Yosef Kahaneman, 1886- 1969) once gave a brilliant interpretation to a famous Gemara. The Talmud [Megilla 3b] mentions that when Yehoshua was encamped during the siege of Jericho, an angel confronted him with a drawn sword. Yehoshua queried the angel as to whether he was friend or foe. The angel identified himself as follows: “I am an angel of the L-rd of Hosts; I have come now.” The Talmud explains that a dialog took place. The angel informed Yehoshua that he committed two sins of negligence: (a) he did not bring the daily sacrifice that day and (b) he neglected his study of Torah that night. Yehoshua asked for which of the two sins he was being held accountable and the angel responded “I have come now” e.g. — for the current sin, that of failing to study Torah.
Tosfos identify the linkage between the words “ATA ba’si” and the failure to study Torah, by quoting the verse “v’ATA kisvu lachem es haShirah haZos” (and NOW record for yourselves this Song — referring to Torah) [Devorim 31:19].
The Ponevezher Rav asks why the Angel used such an obscure reference, rather than telling Yehoshua outright — “I have come because of your failure to study Torah?” The Ponevezher Rav answers that when a person is fighting a battle and is in the middle of a siege, there are a million excuses not to learn. “I’m busy”, “I’m worried”, “I have things on my mind.”
What is the reason why a person must continue to learn, regardless of the circumstances? Because of the phenomenon alluded to in the verse “And now write for yourselves this Shirah [Song]”. Torah is a Shirah that has no beginning and no end. It has no time. It has to be learned every place and under all circumstances. It is that endless expression of what a person is supposed to be all about. Yes you are tired, and worried, and busy, and fighting a war. But “NOW I have come”. There is never an excuse not to learn. Torah is not confined to time or space. It extends toward infinity, like a Shirah.
(from Torah.org)