'Three' in the Bible

‘When you enter the land and plant all kinds of trees for food, then you shall consider their fruit forbidden. For three years the fruit shall be forbidden to you; it shall not be eaten.

It is immoral and shameful if a man marries a woman and her mother; all three shall be burned in fire, so that there will be no immorality among you.

then [this is My answer:] I will order My [special] blessing for you in the sixth year, so that it will produce [sufficient] crops for three years.

But if the child is between one month and five years of age, then your valuation shall be five shekels of silver for the male and three shekels for the female.