'Necessary' in the Bible

This is the law for the man who has the disease of the leper on him, and who is not able to get that which is necessary for making himself clean.

And when he has done whatever is necessary to make the holy place and the Tent of meeting and the altar free from sin, let him put the living goat before the Lord;

And the man on whose head the holy oil has been put, and who has been marked out to be a priest in his father's place, will do what is necessary to take away sin, and will put on the linen clothing, even the holy robes:

But if he gives his field after the year of Jubilee, the amount of the money will be worked out by the priest in relation to the number of years till the coming year of Jubilee, and the necessary amount will be taken off your value.