God gave Israel various laws to keep in order to demonstrate holiness. However, the question remains: Is the church required to keep these laws in order to be holy? The Westminster Confession of Faith (19.4) provides a helpful answer: To them [Israel] also, as a body politic, He gave sundry judicial laws, which expired together with the State of that people; not obliging any other now, further than the general equity thereof may require.
In other words, when Israel ceased to exist—that is, when it no longer had a land, a temple, a capital city, and so forth—these laws ceased to function. This does not mean that Christians are not required to be holy. However, evidence of holiness is no longer expressed in prohibiting the use together of two kinds of cloth. Christians are to be holy by loving their neighbours as themselves, but the evidence of that is not leaving a border around one's field. As Wenham remarks, the detailed application of these imperatives may change from age to age, but the fundamental principles of holy living remain unaltered.
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37 And you shall observe all my statutes and all my rules, and do them: I am the LORD.”