Some sacrifices are requirements and others are volunteer offerings. Regarding the volunteer offerings the Torah stresses once more: it shall be an unblemished male from the cattle, the sheep, or the goats. Whatever has a defect you shall not bring forward, for it will not be acceptable…Sforno explains that when we volunteer something, there is a temptation to think that anything is good enough. And therefore the Torah instructs us that even what we volunteer must be “unblemished”