There’s a famous sentence used as an example of why learning sarf, especially irregular sarf, is important:
مَنْ قَالَ قَالَ اللهُ فَقَدْ كَفَرَ
At first glance, you may think this says “whoever says ‘Allah said’ has disbelieved.” However, in irregular sarf, the weak letter could be either a و or a ي.
So for the second قَالَ, if you use the root ق ي ل, then it makes sense:
Now your translation is: “whoever says ‘Allah took a nap’ has disbelieved.” And that makes sense.