Charity, Virtue that Gives What is Possesses --Aquinas

Of the three theological virtues, which are the greatest of all virtues, charity is the one that gives what it has, it is the virtue which is closest to its object.

Faith is knowledge of things unseen.

Hope is confident expectation of the fulfillment of what is promised.

Charity is gift of self, giving what one possesses, the only thing that one really has, one's own self, which he has received, and continues to receive, from the End of all Goodness, Christ, God.

Charity is, therefore, the greatest virtue in its proximity to the object to which the virtue is ordered. It is one with the object as the end to which it is ordered. 

Nam aliae important in sui ratione quandam distantiam ab obiecto, est enim fides de non visis, spes autem de non habitis. Sed amor caritatis est de eo quod iam habetur, est enim amatum quodammodo in amante, et etiam amans per affectum trahitur ad unionem amati; propter quod dicitur I Ioan. IV, qui manet in caritate, in Deo manet, et Deus in eo. (Summa Theologica I-II, q.66, a.6, c)

Here is the full passage in English, the Aquinas Institute translation. 

[T]he greatness of a virtue, as to its species, is taken from its object. Now, since the three theological virtues look at God as their proper object, it cannot be said that any one of them is greater than another by reason of its having a greater object, but only from the fact that it approaches nearer than another to that object; and in this way charity is greater than the others. Because the others, in their very nature, imply a certain distance from the object: since faith is of what is not seen, and hope is of what is not possessed. But the love of charity is of that which is already possessed: since the beloved is, in a manner, in the lover, and, again, the lover is drawn by desire to union with the beloved; hence it is written (1 John 4:16): He that abideth in charity, abideth in God, and God in him.

This is also discussed earlier in the Summa regarding the distinction of the theological virtues.. 

In II-II, q.17, a.6.

A virtue is said to be theological from having God for the object to which it adheres. Now one may adhere to a thing in two ways: first, for its own sake; second, because something else is attained thereby. Accordingly charity makes us adhere to God for His own sake, uniting our minds to God by the emotion of love.

On the other hand, hope and faith make man adhere to God as to a principle wherefrom certain things accrue to us. Now we derive from God both knowledge of truth and the attainment of perfect goodness. Accordingly faith makes us adhere to God, as the source whence we derive the knowledge of truth, since we believe that what God tells us is true: while hope makes us adhere to God, as the source whence we derive perfect goodness, i.e., insofar as, by hope, we trust to the Divine assistance for obtaining happiness.

God is the object of these virtues under different aspects, as stated above: and a different aspect of the object suffices for the distinction of habits...

Hope makes us tend to God, as to a good to be obtained finally, and as to a helper strong to assist: whereas charity, properly speaking, makes us tend to God, by uniting our affections to Him, so that we live, not for ourselves, but for God.

Respondeo dicendum quod virtus aliqua dicitur theologica ex hoc quod habet Deum pro obiecto cui inhaeret. Potest autem aliquis alicui rei inhaerere dupliciter, uno modo, propter seipsum; alio modo, inquantum ex eo ad aliud devenitur. Caritas igitur facit hominem Deo inhaerere propter seipsum, mentem hominis uniens Deo per affectum amoris.

Spes autem et fides faciunt hominem inhaerere Deo sicut cuidam principio ex quo aliqua nobis proveniunt. De Deo autem provenit nobis et cognitio veritatis et adeptio perfectae bonitatis. Fides ergo facit hominem Deo inhaerere inquantum est nobis principium cognoscendi veritatem, credimus enim ea vera esse quae nobis a Deo dicuntur. Spes autem facit Deo adhaerere prout est nobis principium perfectae bonitatis, inquantum scilicet per spem divino auxilio innitimur ad beatitudinem obtinendam.

Deus secundum aliam et aliam rationem est obiectum harum virtutum, ut dictum est. Ad distinctionem autem habituum sufficit diversa ratio obiecti...

...[S]pes facit tendere in Deum sicut in quoddam bonum finale adipiscendum, et sicut in quoddam adiutorium efficax ad subveniendum. Sed caritas proprie facit tendere in Deum uniendo affectum hominis Deo, ut scilicet homo non sibi vivat sed Deo.

 

 

 

Three passages which readily come to mind are the love of the bad woman for Jesus, the widow's mite and the rich young man.

"She loves much because she has been forgiven much, or, she is forgiven much because she loves much! (Luke 7:47) 

She gives more than the rest, all of her substance. (Mark 12:41-44)

He is called to give everything in order to be able to follow the Lord and goes away sad "because he has many possession". (Matthew 19:22)

Then, there is also the passage of Mary. "Mary has chosen the better part, and it will not be taken from her", which, in the Traditional Latin Mass is a passage which is fittingly used in reference to Our Lady, for the Feast her Assumption. (Luke 10:42)