Deuteronomy 14:22
Make an offering of ten percent, a tithe, of all the produce which grows in your fields year after year.

Deuteronomy 14:25
exchange your tithe for money and take the money to the place GOD, your God, has chosen to be worshiped.

Malachi 3:10
Bring your full tithe to the Temple treasury so there will be ample provisions in my Temple. Test me in this and see if I don't open up heaven itself to you and pour out blessings beyond your wildest dreams.

Plus, remember how God blessed the lady who gave all she had, and saw her money as more meaningful than the rich Pharisees who gave to be seen by men.

I don't think it's how much you give that matters. It's your heart that matters when you give.

10% isn't set in stone in the Bible, but it's a good starting point.