Explanation of Ibn Malik's (may Allah have mercy on him) statement: "And rub was deleted, so it declined after bal *** and fa, and after waw this usage became common."

The Shaykh : He says:
"And rub was deleted, so it declined after bal *** and fa, and after waw this usage became common"
Ibn Malik says: "rub was deleted". From what was it deleted? From the speech. It declines while being deleted, but only after bal, fa, and waw. These are three letters after which rub is deleted, yet its effect remains after these three letters: after bal, fa, and waw. However, it is more frequent after waw. For this reason, he said:
"and after waw this usage became common"
"Shi'a" means it became frequent. An example after bal is: you say, "I did not see a sinful man, but rather a righteous man I met," meaning: "but rather, perhaps a righteous man I met." Here, it declined while being deleted after bal. Fa is also deleted after fa, causing declension, as the poet said:
"So, one like you, pregnant, has come, and a nursing woman *** so I distracted her from one who wears amulets and wanders"
The evidence is his saying: "So, one like you, pregnant", meaning: "So, perhaps one like you, pregnant, has come." Here, rub functioned while being deleted.
Likewise, after waw, rub is deleted and functions after waw, as the poet said:
"And a night like the waves of the sea, which cast its folds *** upon me with all kinds of worries to test me"
"And a night like the waves of the sea" implies: "And perhaps a night"
"like the waves of the sea, which cast its folds *** upon me with all kinds of worries to test me"
Now, rub can enter with "ma" (no) to negate its effect, or perhaps it does not negate it. It functions when mentioned and functions when deleted after three letters: after bal, fa, and waw. Which is the most frequent?
The student: Waw.

The Shaykh : Waw, then fa, then bal. The least frequent is bal.