Tithe: Gratitude for What's Given...Not peanuts.
Leviticus 27:30 “Every tithe of the land, whether of the seed of the land or of the fruit of the trees, is the LORD's; it is holy to the LORD. (ESV)
We must do the expected——God had already ordered Israel to give Him the firstborn and the tithes. It is God's special claim for redeeming them from Egypt (Exod. 13:2; 22:29–30). This was not an Israelite initiative. The firstborn already God's (Lev. 27:26).
This expectation of God also applies to a tithe of crops and herds (Lev. 27:30–33). Look at the bigger picture: God has given Israel much land. Israel should reciprocate by giving God the tithes (out of an attitude of appreciation for blessings already bestowed), rather than giving motivated by the expectation of more blessings to come.
Technicalities aside (vv. 31-33), God still expects us to today to put into action our internal gratitude with the external act of tithing.
The New Testament (NT) does not fix the percentage of the tithe. However, in a post-NT era where we can look back and see OT Exodus actualised in Jesus' salvation and understand fuller revelations of God's grace, shouldn't the OT tithe (10%) give more than a hint of the percentage and size of the tithe that should apply to us?