What does it mean to love His commandments with a whole heart?

Prophet David says in Psalm 118, “Behold, how I have loved thy commandments...” What is meant by this? Blessed Theophylact points out that David “does not simply say, I observed the commandments, but rather I loved them, although, nothing forced me to fulfill them.”

Most of us can’t really say we love His commandments. We may say we love God, but His commandments seem like something difficult, a burden, something we must force ourselves to follow. Perhaps this is only an indication of a weak faith and a limited love of God. David is teaching us that to really love God with our whole heart we also must learn to love His commandments.

Saint Theophan clarifies David’s view. Speaking as David he writes:

The commandments lie at the bottom of my heart, at the very sources of life, and are involved in all its manifestations. I love not only deeds according to the commandments, but the very moral purity required by them, the very perfection of life expressed by them. I love not only the deeds of humility, but humility itself, not only abstention from bursts of anger and impurity, but meekness itself and chastity, not only the deeds of mercy, but mercifulness itself—and so forth.

To love His commandments we must love the "very moral purity required of them." We also must love path to purification of our heart that enables us to live them. It’s more than the values that result from a God-pleasing life. We love the order and perfection they bring, the “moral purity,” the “humility”, the “meekness” that is necessary to live by them. This love develops when the commandments are contained in our heart and we are able to live them without effort. They are no longer forced. They become our natural habit, our way of life. Granted it takes a struggle to reach this state, but as we learn humility and to trust  in God we find this struggle results in love of the commandments themselves, the purity they entail, and the path essential to gain them in our life. 

This love of commandments is possible because the virtues they teach are already in our being. Saint Theophan explains,

Created in God’s image, we carry in ourselves the seeds of all God’s qualities of goodness. And they alone would have shone in our hearts, if the passions that darken, enshroud and distort them had not been grafted on to us by the Fall. The passions are the reason that there is in us a coldness towards virtues, an opposition to, and finally a turning away from them. Perhaps if there had not been God’s commandments, the passions would have led us so far as to drive every virtue from the face of the earth.

This need for love of God' commandments is key to our understanding the spiritual life. We find living by the commandments is difficult because our hearts are filled with passions. It’s not because we are inherently incapable, but that we let our heart be darkened and overtaken by them. The virtues needed to love the commandments are in us, We just have to give them the freedom to become our normal behavior. When we say the commandments are in our heart, it means they become the object of our love and we cannot think of being without them. We love the way of life they bring, and the virtues that make them natural in us. 

When we are able to purify the heart by taming the passions then the commandments stir up in us a life of virtue without effort. 

Saint Theophan puts it this way:

The commandments having been heard, enter in by the hearing, and there they stir up the remembrance of virtues, and of the brightness of the state into which they put a person, in contrast to the darkness of the passions. This remembrance disposes us to submit to the commandments, for the power  contained in them to return us to the lost but desired and bright spiritual state—and we do submit. At first, this submission is both called forth and supported only by the expectation of spiritual good from the commandments, and is effected by an effort of the will. But steadfastness in filling them, the slaying of the passions, quickens in the heart the virtues suppressed by them, returns the quickened ones, and allows the sweetness of those returned to be tasted. This is experienced sweetness of virtues draws the heart to it and makes it inalienable, because it is not coming from the outside, but radiates from the inside and envelopes the heart. From this comes love.

The path to a God-pleasing life based on following God’s commandments dose not happen all at once, but gradually. We submit to them and with Gods help we are purified. When we act through the synergistic efforts of our own effort and God’s grace, participate in the sacramental life in His Church, we step-by-step attain the perfection that Jesus came to show us by His example. When perfected we too will loudly proclaim how we love His commandments,

Reference: Psalm 118: A Commentary by Saint Theophan the Recluse, pp 319-320.