What is the significance of the fact that our ancestors left Egypt "in the month of spring"?
Rashi: Even though we already know that our ancestors left Egypt in Nisan, the Torah is pointing out Hashem's loving-kindness in taking us into the desert in a month that is neither excessively hot nor excessively cold, and in which it does not rain. 1
Ramban (in Pasuk 2) and Seforno: That is why the Torah commands us 2 to ensure that Pesach falls in the spring, 3 by fixing a leap-year when necessary. 4
R. Bachye: "Chodesh ha'Aviv" is synomymous with the barley harvest 5 . All Shalosh Regalim coincide with specific season ? Pesach with the barley harvest, Shevu'os with the wheat harvest and Succos with the ingathering of the crops from the field. 6
Maharal: Refer to 12:2:4.1:1 & 12:15:3.1:1.
See also Tehilim 68:7 and commentaries. Toras Avigdor (Parshas Bo, citing the Saba of Slabodka) - We should appreciate that we left when it was comfortable to travel. Genuine constant happiness comes through appreciating 'small' things in life that most people take for granted - air, water, sight, ability to walk, shoes ....
See Pasuk 10 "Veshamarta ... le'Mo'adah" Refer also to Devarim 16:1:1:1.
Seforno: As it did that year.
See R. Bachye, who explains the word "Aviv" in this context.
R. Bachye: Which explains why we say "Mekadesh Yisrael ve'ha'Zemanim", and not 've'ha'Mo'adim'.
