Or HaChaim on Ki Sisa 31:12

English: ויאמר ה׳ אל משה , G'd said to Moshe, etc. We have to examine why the Torah changed here to using the word ויאמר when describing G'd as speaking to Moshe whereas all the time He was described as וידבר , speaking in a stern voice. I have seen a comment by our sages in the Mechilta according to which the term ויאמר ה׳ indicates that G'd did not speak to Moshe through an intermediary, i.e. angel, but directly. If so, we must still analyse what change had occurred since 31,1 where G'd was still reported as speaking through an intermediary, i.e. וידבר ה׳ אל משה לאמר . Not only that, but why did the author of the Mechilta wait until here to give us this information? This should have been explained