From the Attributes of Allah is that He speaks with a speech that is pre-existent. He causes whomsoever He wills to hear it. Musa heard it from Him without there being any intermediary. Jibreel heard it, as well as whomever He permits from His angels and messengers. He, the One free from all defects, will speak to the believers in the Hereafter and they will speak to Him. He will grant them permission and they will visit Him. Allah says:
"And to Musa, Allah spoke directly." [Surah An-Nisaa (4): 164] And Allah says:
"He (Allah) said: 'O Musa, I have chosen you above men by My messages, and by My speaking (to you).'" [Surah Al-Aaraaf (7): 144] And He says:
"Those messengers! We preferred some of them over others; to some of them Allah spoke (directly)." [Surah Al-Baqarah (2): 253]
And He says:
"It is not for any human being that Allah should speak to him unless (it be) by Revelation, or from behind a veil." [Surah Ash-Shuraa (42): 51]
And He says:
"And when he came to it (the fire), he was called by name: 'O Musa! Verily, I am your Lord!'" [Surah TaHa (20): 11-12]
And Allah says:
"Verily, I am Allah! None has the right to be worshipped but I, so worship Me, and establish the prayer for My Remembrance." [Surah TaHa (20): 14]
It is not permissible for anyone to say this (last ayah) except Allah.
Abdullah bin Masood (ra) said: "When Allah speaks through revelation, the inhabitants of the heavens hear His Voice." He reported this on the Prophet.
Abdullah bin Anees (ra) reported that the Prophet (pbuh) said: "Allah will gather the creatures on the Day of Judgment, naked, barefoot, uncircumcised and not having anything with them. He will then call them with a voice that those who are far as well as those who are near will be able to hear: 'I am Al-Malik (the King). I am Ad-Dayyaan (the Recompenser).'"
In some narrations, it mentions that: One night Musa saw the Fire and it overthrew him so he became frightened from it. Then his Lord called to him: "O Musa!" So he responded quickly, being familiar with the voice: "Here I am to serve you! Here I am! I hear Your voice but I do not see Your place (i.e. where you are). Where are You?" He said: "I am above you and in front of you and on your right and on your left." So he realized that this attribute did not befit anyone except Allah. He (Musa) then said: "You are just as You say, my Lord. Do I hear Your speech or the speech of one of Your messengers (angels)?" He said: "No, rather My speech, O Musa."
The Speech Of Allah
The Quran Is The Speech Of Allah
The Believers Will See Their Lord On The Day Of Judgement
The Divine Decree And Ordainment Of Allah
Iman Is Speech And Action
Faith In Everything That The Messenger Informed Of
Muhammad, The Seal Of The Prophets