We begin the third book of the Torah this week, ספר ויקרא. There are many commentaries on the first three words of the Parsha, ויקרא אל משה, that Hashem “called” to Moshe.
Rabbeinu Bechaye describes this “calling” as unique to Moshe Rabbeinu. He makes a comparison to the Prophet Shmuel and the first time Hashem called out to him. Shmuel was still a young boy and was under the care of עלי, the כהן גדול. On two occasions, Hashem called to Shmuel in a dream. Both times he thought it was עלי calling him. It was עלי who understood that it was prophecy that Shmuel was receiving and he helped the young Shmuel deal with this gift that he received.
Rabbeinu Bechaye uses this story to show the greatness of the prophecy of Moshe Rabbeinu’s prophecy as compared to all other prophets.
All other prophets were addressed by way of an angel. Moshe was addressed by Hashem directly and in a conscious state, which made him stand out.
This was what was meant by ויקרא אל משה and this is also to remind us that one of the Thirteen Principles of Faith of the Rambam was that Moshe was the greatest of all prophets.