This question come every now an then.
Browsers and other programs can automatically trigger a copy to clipboard. So you are vising a website and it copies a malicious command to your clipboard. Then you’re on a terminal and are about to paste something from a trusted VM and Booom! Malicious code pasted and executed.
Not safe…
So basically the only way seems to be learn the thing by heart until you never miss it. And then you’ll know you’re Qubes Native™.