Originally from here.

The steadfast love of the Lord never ceases, His mercies never come to an end; they are new every morning.                                                                                 – Lamentations 3:22-23

On the whole, God’s love for us is a much safer subject to think about than our love for Him. Nobody can always have devout feelings; and even if we could, feelings are not what God principally cares about. Christian love, either toward God or toward man, is an affair of the will. But the great thing to remember is that, though our feelings come and go, His love for us does not.                                                                                                              – C. S. Lewis

Love to God is proof against error. For want of hearts full of love, men have heads full of error; unholy opinions are for want of holy affections.                                   – Thomas Watson

Love is not what we commonly make it to be. For many modern Christians, love is an emotional state; it is a word to describe a certain feeling they sometimes have. But in the Scripture, love is not described in this way at all.

Consider the teaching of John on the subject. “By this we know that we love the children of God, when we love God and keep His commandments. For this is the love of God, that we keep His commandments. And His commandments are not burdensome” (1 John 5:2-3).

It would be hard to make the teaching much clearer. Love is doing what God tells you to do in the Scripture, and doing it from the heart with a joyful spirit. We know that we are to do what we are told because the passage says that love is keeping God’s commandments. We know we are to do it joyfully because the commands are not a burden.

This Biblical understanding of love excludes two errors. The first is the error of legalism. The legalist obeys some modified and reinterpreted commands, and does so externally. The problem Jesus had with Pharisees was not that they were too holy, but that they weren’t holy at all. They were hypocrites. They would tithe out of their spice rack, but refused to acknowledge love, mercy, and justice.

Legalism cannot obey all the commands of God, and it cannot do so in a joyful manner. The legalist has to sweat bullets to accomplish what he does, and what he accomplishes isn’t worth anything in the sight of God.

The opposite error is the one of antinomianism. The word literally means “against the law.” This is the error which regards Christian love as nothing more than a vague, warm, blurry benevolence. Love is identified with emotion, and not with doing what you are told to do.

There are two ways to refute this error, and the first is simply the plain statement of our text. Love is keeping commands with a whole heart–nothing more and nothing less.

The second refutation is to consider the consequences of such thinking for Christian morality. Many well-meaning Christians, who are horrified at the decline of morality around us, fail to see that their definition of love is one of the central culprits. If love is an emotion, then is it possible for me to experience true love for another man’s wife? Certainly. And if it is true love, then why should it be denied? There are many who have come to the logical conclusion that it should not be, and even the Christian world is littered with the wreckages of marriages built on the sand of human emotion.

But if love is doing what you are told, and God has told you that another man’s wife is not yours to covet, and not yours to have, then it is impossible for adultery to be “loving.” It doesn’t matter how soaring the emotion.

Now of course this does not mean that the emotional “love” is wrong. It simply means that our emotions are to be protected by our commitment to the law of God. We cannot protect obedience with emotion, but we can protect emotion with obedience.

The two greatest commandments have love for their verb. We are to love God with all that we are and have, and we are to love our neighbors as ourselves. In order to obey these commands, we have to understand what they are telling us to do. And mark it well, they are telling us to do something that can be measured and seen in the external world. And what is that? To the law, and to the testimony! (Isaiah 8:20).

Of love there be two principal offices, one to give, another to forgive.
– John Boys

The saints are the walking pictures of God. If God be our Father, we shall love to see His pictures of holiness in believers; shall pity them for their infirmities, but love them for their graces. . .It may justly be suspected that God is not Father of those who love not His children. Though they retain the communion of saints in their creed, they banish the communion of saints out of their company.                                                     – Thomas Watson

What then shall we say to these things? If God is for us, who can be against us? He who did not spare His own Son, but delivered Him up for us all, how shall He not with Him freely give us all things? Who shall bring a charge against God’s elect? It is God who justifies. Who is he who condemns? It is Christ who died, and furthermore is also risen, who is even at the right hand of God, who also makes intercession for us. Who shall separate us from the love of Christ? Shall tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword?
   As it is written: “For Your sake we are killed all day long; we are accounted as sheep for the slaughter.” Yet in all these things we are more than conquerors through Him who loved us. For I am persuaded that neither death nor life, nor angels nor principalities nor powers, nor things present nor things to come, nor height nor depth, nor any other created thing, shall be able to separate us from the love of God which is in Christ Jesus our Lord.                                                                                                    – Romans 8:31-39

In the passage above, we clearly see the love of God in Christ displayed. Because the love of God for us in Christ was not transient emotion, but rather what He did in the cross, nothing can separate us from that love. Who can fight what God has done? “No one,” the apostle replies.

The redeemed are loved by the Creator, and therefore no thing in all creation is capable of coming between Lover and Beloved. God’s electing love is not something that any creature can withstand. God’s love is inexorable.

Love is the only thing in which we can retaliate with God. If God be angry with us, we must not be angry again; if He chide us, we must not chide Him again; but if God loves us, we must love Him again. There is nothing in which we can answer God again, but love. We must not give Him word for word, but we must give Him love for love.     – Thomas Watson

Affection without action is like Rachel, beautiful but barren.
– John Trapp

In this is love, not that we loved God, but that He loved us and sent His Son to be the propitiation for our sins.                                                                       – 1 John 4:10

You can give without loving, but you cannot love without giving.
– Amy Carmichael

Joy is love exalted; peace is love in repose; long-suffering is love enduring; gentleness is love in society; goodness is love in action; faith is love on the battlefield; meekness is love in school; and temperance is love in training.                                                             – D. L. Moody

But it is doubtless true, and evident from these Scriptures, that the essence of all true religion lies in holy love; and that in this divine affection, and an habitual disposition to it, and that light which is the foundation of it, and those things which are the fruits of it, consists the whole of religion.                                                                        – Jonathan Edwards

He loves but little who tells how much he loves.
– John Boys

Love of man necessarily arises out of love of God. The love of the creature is but the corollary to the love of the Creator. This is what the Christian finds, as a matter of fact. His heart is overcharged with love to God. It finds its way out in love to man. His direct service of God cannot, in the nature of things, go very far. He worships God publicly in His house. He glorifies Him secretly in the constant outpourings of his heart. He gives of his substance to the maintenance of every cause which is God’s cause. But here it ends. God is so mighty, so self-contained, that with all our puny efforts, much cannot be done to serve. So the Christian looks about to see how he is to show his love for God. He soon finds the way. Clearly, it must be by love for his fellow-men.    – John Hooper