A mark which is always set upon Christ's sheep, and never set upon any others!
"And we know that God causes all things to work together for good to those who love God, to those who are called according to His purpose." Romans 8:28
There are some graces which in their vigor are not absolutely essential to the bare existence of spiritual life, though they are very important for its healthy growth. But true love for God must be in the heart—or else there is no grace there whatever. If a man does not love God, then he is not a renewed man. Love for God is a mark which is always set upon Christ's sheep, and never set upon any others.
I have no right, therefore, to believe that I am a regenerated person—unless my heart truly and sincerely loves God. If I have been regenerated, I will not be perfect, but this one thing I can say: "Lord, You know all things. You know that I love You!" When by believing we receive the privilege to become sons of God—we also receive the nature of sons, and with filial love we cry, "Abba, Father!"
There is no exception to this rule! If a man does not sincerely love God—then he is not born of God. As the sun must give forth its light—so must a soul that has been created anew by divine grace, display its nature by earnest affection toward God. You are not born again, unless you love God. Sincere love to God is indispensable!
"If anyone does not love the Lord, he is to be accursed!" 1 Corinthians 16:22