What is the language in which Allaah The Almighty spoke to Aadam (Adam) and to Moosa (Moses), may Allaah exalt their mention?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

Allaah The Almighty informed us in the Quran that He talked to Aadam without mentioning the language He used. He Says (what means): {And We said, "O Aadam, dwell, you and your wife, in Paradise.} [Quran 2:35]. Had there been any benefit in knowing what language He used, it would have been transmitted to us in the Quran or the Sunnah (Prophetic tradition). Hence, we should not tackle issues that are not mentioned in the Sharee‘ah (Islamic law).

The language of Moosa was Hebrew. Allaah The Almighty revealed to him in the language that he understood. Ibn Taymiyyah mentioned that Allaah The Almighty revealed to Moosa in Hebrew, and to Muhammad, sallallaahu ‘alayhi wa sallam, in Arabic. 

Allaah Knows best.