The Scofield Bible Commentary, by Cyrus Ingerson Scofield, [1917], at sacred-texts.com
keep the passover
Compare the order of the feasts in Leviticus 23. Here the Passover and Tabernacles are given especial emphasis as marking the beginning and the consummation of God's ways with Israel; the former speaking of redemption, the foundation of all: the latter, or re-gathered Israel blessed in the kingdom. Between, in (Deu 16:9-12) comes the Feast of Weeks -- the joy of a redeemed people, anticipating a greater blessing yet to come. It is, morally, (Rom 5:1); (Rom 5:2).
Abib
First monththat is, April.
grove
The groves (Hebrew, "Asherim") so often mentioned in the Old Testament were devoted to the worship of Ashtereth, the Babylonian goddess, "Ishtar", the "Aphrodite" of the Greeks, the Roman, "Venus".
(See Scofield) - (Jdg 2:13).