Rabbi Ari Neuwirth in Parashat Nitzavim: Why a Song? says that Torah is called Shirah (Song) in our parsha because no mitzvos can be taken out and none can be added to our perfect Torah.
There is a Russian idiom "из песни слова не выкинешь", literally "one cannot throw a word out of song".
The meaning is that "when telling a story, one may not omit even unpleasant/unsavory details", or, more broadly, "a coherent structure loses its coherence when critical parts are removed".
Is there a Hebrew analogue of this expression?