Question : Why was it forbidden to people who had any problem offer to God?

Could you help me to understand this versicles?

Vayicrá 21: 19-21

19 - Or a man that is brokenfooted, or brokenhanded,
20 - Or crookbackt, or a dwarf, or that hath a blemish in his eye, or be scurvy, or scabbed, or hath his stones broken; {a dwarf: or, too slender}
21 - No man that hath a blemish of the seed of Aaron the priest shall come nigh to offer the offerings of the LORD made by fire: he hath a blemish; he shall not come nigh to offer the bread of his God.

Thanks

Answer : Why was it forbidden to people who had any problem offer to God?

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