John Gill Commentary Joshua 23:16

"When ye transgress the covenant of Jehovah your God, which he commanded you, and go and serve other gods, and bow down yourselves to them; then will the anger of Jehovah be kindled against you, and ye shall perish quickly from off the good land which he hath given unto you." — Joshua 23:16 (ASV)

When ye have transgressed the covenant of the Lord your God ,
which he commanded you
The law, so called, and the several precepts of it, particularly those which relate to the faith and worship of the one only true God; see (Exodus 24:7Exodus 24:8) ;

and have gone and served other gods, and have bowed down yourselves
unto them ;
been guilty of idolatry, of having and worshipping other gods, which are no gods, with or besides the God of Israel, see (Joshua 23:7) ;

then shall the anger of the Lord be kindled against you ;
nothing being more provoking to him than idolatry, he being a jealous God of his honour and worship:

and ye shall perish quickly from off the good land which he hath given
unto you ;
as they did at the time of the Babylonish captivity, and at the last destruction of Jerusalem by the Romans.