“But the Lord said to Moses and Aaron, ‘Because you have not believed Me, to treat Me as holy in the sight of the sons of Israel, therefore you shall not bring this assembly into the land which I have given them.'” Num. 20:12
God said to Moses and Aaron that He would be treated holy in the sight of the sons of Israel. Because Moses struck the rock instead of doing what God commanded, speak to the rock, there was rebellion in that act of striking the rock. The words of God to Aaron and Moses are similar to the words that God spoke after he destroyed Nadab and Abihu who brought Strange Fire into the Tabernacle. They did not treat God is Holy by their sin. We see once again in the scriptures that God is very serious about being obeyed according to his instructions. We are not to add to or take away from what he says to do. This is why when He says to partake of the Lord’s Supper we only have bread and fruit of the Vine. This Is why when He says to sing we only sing and do not add any other form of music. This Is why when God says to immerse people for remission of sins we do not sprinkle or pour water over them. God specifically says how to do things and that is the way it is to be done. And in so doing we treat Him as holy and we revere His word. It’s a matter of faith.