According to Deut 6:5, we are to love God.  But why love God?  We love God because:

The law commands us to love God – Deut 6:5; Matt 22:37 – when Jesus was asked about the great commandment in the law, he replied, “Thou shall love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind.”  We love him because he told us to love him.

God first loved us – 1 Jn 4:19, 10 – God made the first move.  God commendeth his love toward us, in that, while we were yet sinners, Christ died for us,” [Rom 5:8].  “God so loved the world that he gave his only begotten Son…” [Jn 3:16].  There has never been a greater demonstration of love than the love that God showed us when he gave us his Son.

God has forgiven us so much – Lk 7:40-47 – sometimes we look back on our past with so much regret that we become overwhelmed with our wretchedness rather than with God’s goodness and love.  Don’t let the sin of your past be magnified in your thoughts.  Instead, magnify your love for God because he has forgiven us off all that sin.  Those of us who have been forgiven the most should love him the most.

The Holy Spirit directs us to love God – 2 Tim 1:7; 2 Thes 3:5; Gal 5:22 – because we are saved, the Holy Spirit indwells us.  And from him we receive the spirit of love which directs our hearts into the love of God.  Love is the fruit of the Spirit.  And as we grow in grace and in the knowledge of the Lord Jesus Christ, the love of God is shed abroad in our hearts by the Holy Spirit.

God is the better master to love – Matt 6:24 – you are going to serve one master or the other; either mammon or God.  If you have ever tried to serve mammon, you know two things are true.  Mammon is a cruel master and serving mammon results in hatred for God.  When you serve the Lord, you love God and hate mammon.  God is by far the better master.  Serving him is very satisfying and gratifying.  Serving mammon is not.

God makes all things work together for good – Rom 8:28 – “all things work together for good to them that love God…”. When you love God, though you go through bad things and endure hardships and trials, somehow, God always makes all these things work together for good.  And the way God always works these things out causes you to just love him more and more. 

Conclusion: 1 Cor 8:3 when you love God like this, you don’t have to tell anybody; they can tell it.  “If any man love God, the same is known of him.”  Your witness and testimony become real when others can tell that you really love God.