“For I am the Lord your God, and you shall sanctify yourselves and be holy, because I am holy…”
A human being is composed of a Divine soul enclothed in a material body. The soul, which contains a spark of actual Divinity, is the channel that connects us to the Will of Hashem, our Creator and constant source of life.
In order to nurture and guarantee the continuation of this connection, we must behave in accordance with the Divine Will as expressed through the Torah guidelines.
Hashem commanded us to follow 613 commandments, some active commandments that we must fulfil, while others require us to refrain from certain activities and behaviours. In following these laws, we attach ourselves to the Will of our Creator and as such, we actually sanctify our physical body. We become holy.
The material world and Upper worlds function in a manner of cause and effect. While some commandments make sense to our human mind (not committing murder, not stealing, etc.), we cannot fully understand the reason behind certain laws (such as the laws of kashrut). They are beyond human reasoning in this world. When the soul parts from the body and returns Above, the person will see everything clearly.