[1] What caused the souls of the Jewish people to leave their body by Matan Torah
Our sages teach us that at the time that the Torah was given, the souls of the Jewish people expired and that they had to be resurrected with the dew of Torah. What caused the soul of the Jewish people to expire is the fact that at the time that the Torah was given, there was a great revelation of G-dliness that surpasses understanding and wisdom. This level shined upon the souls inner faculties in a revealed fashion with much revelation and intensity. This caused the soul to leave the body, which means that it left its intellectual boundaries and became incorporated and nullified in existence.
[1] Likkutei Torah Bamidbar