"What must I love thee for, then?" Why ought we to love God? Desire for heaven? Fear of hell? The last line of the poem below gives us the answer.
Gerard Manley Hopkins' translation of the poem attributed to Francis Loyola:
"I love thee, God, I love thee—
Not out of hope for heaven for me
Nor fearing not to love and be
In the everlasting burning.
Thou, my Jesus, after me
Didst reach thine arms out dying,
For my sake sufferedst nails and lance,
Mocked and marred countenance,
Sorrows passing number,
Sweat and care and cumber,
Yea and death, and this for me,
And thou couldst see me sinning:
Then I, why should not I love thee,
Jesu so much in love with me?
Not for heaven’s sake, not to be
Out of hell by loving thee;
Not for any gains I see;
But just the way that thou didst me
I do love and will love thee.
What must I love thee, Lord, for then?
For being my king and God. Amen."
That's why we love Him. Because he's been our king. And as a good king he reached out to us, loved us, died for us. This is our Jesus, we love him as our Lord.