Leviticus 19:2
1 The Lord spoke to Moses: 2 “Speak to the whole congregation of the Israelites and tell them, ‘You must be holy because I, the Lord your God, am holy. 3 Each of you must respect his mother and his father, and you must keep my Sabbaths. I am the Lord your God. 4 Do not turn to idols, and you must not make for yourselves gods of cast metal. I am the Lord your God.
Joshua 24:19
19 Joshua warned the people, “You will not keep worshiping the Lord, for he is a holy God. He is a jealous God who will not forgive your rebellion or your sins. 20 If you abandon the Lord and worship foreign gods, he will turn against you; he will bring disaster on you and destroy you, though he once treated you well.” 21 The people said to Joshua, “No! We really will worship the Lord.”
Notes and References
"... In Joshua 24:19 God is presented as holy and jealous. If one looks backwards from Joshua 24, God is explicitly described as holy in only one book, namely Leviticus and especially in the Holiness Legislation ... in Leviticus the first example – in what has traditionally been known as the Holiness Code – of YHWH being described as holy occurs in Leviticus 19:2; this introduces us to the language of holiness, which has obviously given Leviticus 17–26 its name, although the holiness language is found only in chapters 19 to 21 ... Where Achenbach thought that the parenetic frame of the Holiness Legislation was getting rid of Joshua, I would think it could be the other way around. Joshua 24 was leaving the Pentateuch and the Holiness Legislation behind. These verses were added after the Hexateuch project failed and the book of Joshua was removed ..."
Meyer, Esias E. "Leviticus 19:2 and Joshua 24:19: An Example of Literary Allusion?" in Himbaza, Innocent (ed.) The Text of Leviticus: Proceedings of the Third International Colloquium of the Dominique Barthélemy Institute (pp. 179-204) Peeters, 2020