John Gill Commentary Joshua 23:11

"Take good heed therefore unto yourselves, that ye love Jehovah your God." — Joshua 23:11 (ASV)

Take good heed therefore to yourselves
To be upon their guard, and to be watchful, were very necessary to them, that they might not be ensnared by the Canaanites, and drawn aside by them into idolatry, and so apostatize from the Lord and his worship, since their temptations would be many:

that you love the Lord your God ;
which would the most strongly influence and engage them to serve and worship the Lord, and obey his commands, and be the best preservative against idolatry and false worship.