A believer argued that "The Old Testament Law is obsolete per Hebrews 8:13." Is that assumption correct, and how does it reconcile with the calls to set-apart in Leviticus 11:44, 19:2, 20:26, and 1 Peter 1:13-16?

2 Timothy 3:16
Living Bible
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16 The whole Bible was given to us by inspiration from God and is useful to teach us what is true and to make us realize what is wrong in our lives; it straightens us out and helps us do what is right.
Footnotes

1. 2 Timothy 3:16 The whole Bible, literally, “Every Scripture.”