What Sutta uses the simile of "Ornamenting with a Dead Snake? I believe the Sutta has to deal with the proliferation of thought and how allowing that process to run out of control is like adorning one’s ‘self’ with a dead snake.
You may be thinking of AN9.11
Suppose there was a woman or man who was young, youthful, and fond of adornments, and had bathed their head. If the carcass of a snake or a dog or a human were hung around their neck, they’d be horrified, repelled, and disgusted. In the same way, I’m horrified, repelled, and disgusted by this rotten body. Someone who had not established mindfulness of the body might well attack one of their spiritual companions and leave without saying sorry.
On second thought … MN20 is probably a better match for what you were asking:
Now, suppose that mendicant is focusing on some other foundation of meditation connected with the skillful, but bad, unskillful thoughts connected with desire, hate, and delusion keep coming up. They should examine the drawbacks of those thoughts: ‘So these thoughts are unskillful, they’re blameworthy, and they result in suffering.’ As they do so, those bad thoughts are given up and come to an end. Their mind becomes stilled internally; it settles, unifies, and becomes immersed in samādhi. Suppose there was a woman or man who was young, youthful, and fond of adornments. If the carcass of a snake or a dog or a human were hung around their neck, they’d be horrified, repelled, and disgusted. In the same way, a mendicant … should examine the drawbacks of those thoughts …
Yes, that’s the one that came to my mind (MN20).
You are awesome, thank you!