EXOD174 Sanctify firstborn males. If a Jewish woman's firstborn child is a male, the child must be sanctified to Hashem. The same applies to the firstborn male of kosher animals (e.g., cows, goats, sheep) or of a donkey. We must realize that everything in existence belongs to Hashem. Whatever anyone possesses comes from Hashem, Who gives of His great bounty because of His kindness. Therefore, after a person makes great efforts and his toil finally yields fruit, although his first fruits are very dear to him, he immediately parts with them and gives them to Hashem. This reminds the person that whatever he or she possesses actually belongs to the Creator. Another reason for the mitzvah: To remind us of the great miracle that Hashem performed for us when He saved us from the Egyptians by killing their first born.