Sometimes people are driven to give charity out of peer pressure or for some ulterior motive. Usually this is acceptable and even praiseworthy – since the goal is to help the needy and so the motive is less important. The Tabernacle – God’s house – is different. God is not “needy” and therefore the verse states: Whose heart urges him, let him bring it, a donation of the LORD…Netziv explains this verse to be literal. It was not good enough to send a donation, rather, the donor had to bring the donation. This allowed those receiving it to assess whether it was truly from the heart.