A person’s eternal spiritual perfection and holiness depend on performing mitzvas. The eventual redemption also depends on our performing mitzvas, even mitzvas that are not applicable in exile, such as bringing sacrifices to the holy Temple. Although we can’t perform them physically, if we learn the halachas pertinent to these mitzvas it is considered as if we performed them, since we show Hashem how much we yearn for them, as it says, ‘and we will pay oxen with our lips’.