Exodus 30:16
And thou shalt take the atonement money of the children of Israel, and shalt appoint it for the service of the tabernacle of the congregation; that it may be a memorial unto the children of Israel before the LORD, to make an atonement for your souls.
Every Israelite, in addition to the tithe, was to contribute a half shekel as a ransom for his soul. The payment was made when the people were numbered. It was due yearly. The money thus collected was appointed for the service of the tabernacle of the congregation, which is the support of the temple. It helped meet the sanctuary's needs, including necessary repairs and other expenses.
Only the temple shekel was the coin accepted for the service of the sanctuary. At Passover great numbers assembled at Jerusalem from all parts of Palestine and from distant lands, and all foreign coin had to be changed for the temple shekel. Beyond this required amount, large sums were also brought as freewill offerings to be deposited in the temple treasury.