This is one of meany verses that make reference to tithes
Gen 28:22 And this stone, which I have set for a pillar, shall be God's house: and of all that thou shalt give me I will surely give the tenth unto thee.
Here Abraham is being thankful to God and tells God, that out of all, that God has given him (Abraham) he would return to God a tenth.
There is no rule or law that requires this,It will not keep you from being saved, if you don't give. But it may keep an abundent of blessings from you.
Returning part of what God has given us, must be done with a willing heart. It is the sprit in which the gift is given, rather than the amount.
Luk 21:1 And he looked up, and saw the rich men casting their gifts into the treasury.
Luk 21:2 And he saw also a certain poor widow casting in thither two mites.
Luk 21:3 And he said, Of a truth I say unto you, that this poor widow hath cast in more than they all:
Luk 21:4 For all these have of their abundance cast in unto the offerings of God: but she of her penury hath cast in all the living that she had.