(א) וַיִּקְרָ֖א אֶל־מֹשֶׁ֑ה וַיְדַבֵּ֤ר יְהוָה֙ אֵלָ֔יו מֵאֹ֥הֶל מוֹעֵ֖ד לֵאמֹֽר׃
ויקרא אל משה. לְכָל דִּבְּרוֹת וּלְכָל אֲמִירוֹת וּלְכָל צִוּוּיִים קָדְמָה קְרִיאָה, לְשׁוֹן חִבָּה, לָשׁוֹן שֶׁמַּלְאֲכֵי הַשָּׁרֵת מִשְׁתַּמְּשִׁין בּוֹ, שֶׁנֶּאֱמַר וְקָרָא זֶה אֶל זֶה (ישעיהו ו'), אֲבָל לִנְבִיאֵי אֻמּוֹת הָעוֹלָם נִגְלָה עֲלֵיהֶן בִּלְשׁוֹן עֲרָאִי וְטֻמְאָה, שֶׁנֶּאֱמַר וַיִּקָּר אֱלֹהִים אֶל בִּלְעָם (במדבר כ"ג):
ויקרא אל משה AND [THE LORD] CALLED UNTO MOSES — All oral communications of the Lord to Moses whether they are introduced by דבר or by אמר or by צו were preceded by a call (to prepare him for the forthcoming address) (Sifra). It is a way of expressing affection, the mode used by the ministering angels when addressing each other, as it is said (Isaiah 6:3) “And one called unto another [and said, Holy, holy, holy is the Lord of hosts]”. To the prophets of the nations of the world, however, God revealed himself in a manner which Scripture describes by an expression ordinarily used for denoting events of a casual character and of uncleanness, as it is said, (Numbers 23:4) “and God happened to meet (ויקר) Balaam” (the term ויקר, from the root ,קרה, is connected with מִקְרֶה which denotes “chance”, “occurrence”, and has also the meaning of “uncleanness”, by analogy with Deuteronomy 23:11: לא יהיה טהור מקרה לילה) (cf. Bereishit Rabbah 52; Leviticus Rabbah 1).
א' דויקרא זעירא שמשה לא רצה לכתוב אלא ויקר כדרך שנא' בבלעם כאלו לא נראה לו השם אלא במקרה ואמר לו הקב''ה לכתוב גם באל''ף וכתבה קטנה. ויקרא אל משה.
The alph of vayikra is small, since Moses wanted to write vayikar (he happened), as it is said of Bilaam, as if God had only happened upon him accidentally. God told him to write an aleph, so he wrote it small.
The foregoing enables us to understand the Zohar who comments on Leviticus 1,1: "He spoke to him out of the Tent of Meeting," that G'd spoke from the interior, or depth of the Tabernacle, informing Moses that the Children of Israel would be prepared to sin and how the Temple would be destroyed as a result. This is why the Torah writes here ויקרא, without identifying who called.
Sfat Emet on Vayikra, 1901
The alpeh in vayikra is small. Moses received the whole Torah during his 40 days & nights in heaven. If so, why were these sections spoken in the tent of meeting, below? The Israelites weren't ready to receive the Torah that Moses received in heaven, which is in the aspect of "large aleph." And this teaching was in constricted consciousness compared with the level of Moses, because to him [fear of God] is a small thing. And this is the meaning of "He said...to say." This was learning to speak to the Israelites. This is the meaning of "because of you He is speaking with me:" in that way and path that the Israelites will be able to receive. This itself is the idea of the sacrifices, as it is written "Happy [is the one who] you favor and draw near." Favor is the aspect of Moses His favorite. The Israelites were ready at the giving of Torah, when they were chosen to be "His people, a portion of Him." They themselves were really the Torah, as it is written "Torah, God, and Israel are all one." But when we fell from this level, we needed to draw ourselves near with sacrifices. And this is something which exists in fact.
Avi Weiss, "The small aleph of vayikra: Infinite love between God and the Jewish people"
Rav Shlomo Carlebach often told the story of the Munkatcher passport. In this story his uncle asked the Munkatcher Rebbe for a passport to travel from Munkatcher to Berlin just before WW II. Considering the climate of the times the request seemed impossible to fulfill. After many hours, the Rebbe emerged from his private chambers and gave him an empty piece of paper soaked with tears with which Shlomo's uncle was escorted everywhere in Germany with great honor.
Rav Shlomo explained that the Munkatcher passport surfaces over and over in our lives. When a bride walks around the groom, they give each other the Munkatcher passport. When children are born they close their eyes and cry, giving to and receiving from their parents the Munkatcher passport. And when we stand near the Kotel to pray before the Lord, we do so with the Munkatcher passport. And, concluded Rav Shlomo, when we begin the Talmud, we start on the second page — daf bet. Where is daf aleph, the first page? It is empty, absolutely empty. It is the Munkatcher passport.
Rav Shlomo never explained what the Munkatcher passport meant, but for me it represents infinite love. Hence the aleph of vayikra is small to remind us of the importance of approaching God with daf aleph, with the Munkatcher passport — symbolic of the unconditional love that we ought to have for God and that God has for us and that we should all have for each other.