Deuteronomy 6:5 and thou shalt love the Lord thy God with all thine heart, and with all thy soul, and with all thy might.
This was not a suggestion. It was a direct command from God to Moses. He was taking care of the vast host of Israel and wanted them to respect Who He is. To love God with all your heart is not a feeling that comes and goes. It’s everything internal that says you choose to love and obey Him. Soul is the intertwining of the mind and heart. It’s who we are on the inside. And might implies overwhelming power or strength. So we need to love God with every fiber of our being. He is worthy. He is King of kings and Lord of lords.