Explanation of the author's statement: "And among the proofs of the Sunnah is the saying of the Prophet (peace and blessings be upon him): 'Allah the Exalted says: O Adam.'"

The Shaykh : He said: "And among the proofs of the Sunnah is the saying of the Prophet (peace and blessings be upon him):

God most high will call Adam and he will reply, "At Thy service and at Thy pleasure

يقول الله تعالى : يا آدم. فيقول : لبيك وسعديك

Mishkat al-Masabih 5541

".
This is on the Day of Resurrection when Allah says: O Adam, and He directs the call to him with letters. O Adam, did he hear it or did he not hear it? If he heard it, then it is with a voice.
"

'O Adam!' Adam will reply, 'Labbaik wa Sa`daik! '

يا آدم فيقول : لبيك وسعديك

Sahih al-Bukhari 7483

"
What does "Labbayk" mean? It means: response and steadfastness in your obedience, for the meaning of the talbiyah is response, persistence, and steadfastness in a matter.
We say: The meaning of "Labbayk" is response to what you called me to.
"Wa sa'adik"? They said: "Sa'adik" is a verbal noun meaning to make happy, i.e., I ask you to make me happy.
It was also said: The meaning of making happy is assistance; its meaning is assistance. From this comes their saying in the pre-Islamic age of ignorance regarding mourning: So-and-so assisted so-and-so, meaning: she helped her with her mourning.
And His saying: "

Then He calls out with a voice

فينادي بصوت

" He calls out with a voice. Look, He said He calls out with a voice. The word "with a voice" is, with respect to its agent in the verb, right? It is only for emphasis, because a call cannot be made except with a voice.
He says: "

Allah Commands you to take out the mission of the Hell Fire from your offspring.

إن الله يأمرك أن تخرج من ذريتك بعثاً إلى النار

Sahih al-Bukhari 7483

" Does He bring them out or not? He brings them out, but how does He know them? He knows them by their marks, because the marks of the disbelievers, may Allah protect us from that, on the Day of Resurrection are distinguished and made clear.
Is there in this hadith evidence that the speech of Allah is by His will?
The student: When He wills a thing, He says to it, "Be," and it is.

The Shaykh : No, I want [evidence] in the hadith? , how is that? Because He speaks on the Day of Resurrection, so it is connected to His will.
And is there in it evidence that it is with letters? Yes, because the content of the speech is letters.
And is there in it evidence that it is with a voice? It is clear, but this voice does not resemble the voices of the created beings.