V'Zot HaBrachah

Giving the Torah, God “...came with the myriads of the holy angels...”  - the word “came,” however, is in Aramaic. The reason for using Aramaic is to hide from the holy angels, so that they would not accuse the Jews and thus prevent the giving of the Torah.

By the same token, when God “...appeared to Abraham...”,  the word “appeared” is in Aramaic. The reason for using Aramaic is that Abraham was not yet circumcised, and God wanted to conceal His appearance to Abraham from angels, so that they would not accuse him.

So too, in Isaiah, when God calls to repentance, saying “...Return, and return again...” - this phrase is in Aramaic. The repentant gets forgiveness from the hidden place under the throne of God, and the Aramaic hides this, so that the angels do not prevent his acceptance.