I will not start with a direct proof text, here. I am going to a text which has been claimed to refute these, rather.
Luke 17:5 And the apostles said to the Lord; Increase our faith.  And the Lord said: If you had faith like to a grain of mustard seed, you might say to this mulberry tree, Be thou rooted up, and be thou transplanted into the sea: and it would obey you.  But which of you having a servant ploughing, or feeding cattle, will say to him, when he is come from the field: Immediately go, sit down to meat:  And will not rather say to him: Make ready my supper, and gird thyself, and serve me, whilst I eat and drink, and afterwards thou shalt eat and drink?  Doth he thank that servant, for doing the things which he commanded him?  I think not. So you also, when you shall have done all these things that are commanded you, say: We are unprofitable servants; we have done that which we ought to do.
- Comment by Challoner:
-  Unprofitable servants: Because our service is of no profit to our master; and he justly claims it as our bounden duty. But though we are unprofitable to him, our serving him is not unprofitable to us; for he is pleased to give by his grace a value to our good works, which, in consequence of his promise, entitles them to an eternal reward.
- Collected comments in Haydock:
Ver. 5. Increase our faith. The disciples having heard our Saviour inculcating maxims hard to flesh and blood, such as avoiding scandal, and forgiving our enemies, humbly beg their faith may be increased, that they may be able to comply with these maxims; for they had heard Christ say, that every thing was possible to him that believed. (Theophylactus) --- Christ compares faith to a grain of mustard seed; because, though the grain be small, it is nevertheless stronger than most herbs. (St. Chrysostom)
Ver. 6. To this mulberry-tree. In St. Matthew, (xvii. 19.) we read, to this mountain. Christ might say both at different times. (Witham)
Ver. 7. The design and end of this parable is to shew that, rigorously speaking, we are useless servants with regard to God. This sovereign Master has a right to exact of us every kind of service, and to make us apply ourselves to any task he may think proper, without our having any reason to complain either of the difficulty, trouble, or length of our labours; we are entirely his, and he is master of our persons, time, and talents. We hold of him whatever we possess, and woe to us if we abuse his trust, by applying our talents to any use contrary to his designs. But though he be Lord and Master, he leaves our liberty entire. If he produces in us holy desires, if he works in us meritorious actions, gives us virtuous inclinations and supernatural gifts, he sets to our account the good use we make of them; and in crowning our merits, he crowns his own gifts. (St. Augustine, lib. ix. Confes. and Serm. 131.) (Calmet)
Ver. 10. Unprofitable servants. Because our service is of no profit to our Master; and he justly claims it as our bounden duty. But though we are unprofitable to him, our serving him is not unprofitable to us; for he is pleased to give, by his grace, a value to our good works, which, in consequence of his promise, entitles them to an eternal reward. (Challoner) --- The word useless, when joined to servant, generally means a servant from whom his master does not derive the service he has a right to expect; as in St. Matthew xxv. 30. Here the word is taken in a less odious sense. It means a servant who does not testify sufficient zeal and ardour in his master's service, who is not very eager to please him. With regard to God, we are always useless servants, because he wants not our services; and without his assistance, we can neither undertake nor finish any thing to please him. (Calmet)
Why did I come here?
Well, someone claimed that Anglicanism does believe Eucharist is a propitiatory sacrifice, I looked up 39 articles of religion and found, at least 39-articles Anglicanism does not do that (which is of course blatant heresy, condemned by Trent and by Tradition, by Hebrews "we have an altar" and by Malachi 1:11.
Now, while looking up the 39 articles, I also found this, which is clearly questionable exegesis, not to say eisegesis:
XIV. Of Works of Supererogation
Voluntary Works besides, over, and above, God's Commandments, which they call Works of Supererogation, cannot be taught without arrogancy and impiety: for by them men do declare, that they do not only render unto God as much as they are bound to do, but that they do more for his sake, than of bounden duty is required: whereas Christ saith plainly, When ye have done all that are commanded to you, say, We are unprofitable servants.
I would say that those who work miracles and tell mulberry trees to root themselves up and they do so are on the contrary really obedient to Christ who here said one "might" but does not command the apostles to do it.
Mustard Seed Faith is itself a supererogatory work over and above the faith in the articles of the Apostolic or Nicene Creed and their explanations in other dogma defined by the Church.
And Christ was recommending it, just after saying the "attitude formula" which Anglicans in Elisabeth's time claimed excluded supererogatory works.
The actual proof texts are there in any Catholic Catechism. Especially, selling all one has and giving it to the poor is mentioned twice over as such a thing. You can laud a man for doing it, you cannot blame me for not doing it. The rich man is told, not that he must do that to be saved, but that he must do that to be perfect. Ananias and Sapphira who pretended to comply with this supererogatory work were told it was such a thing, that they had been free to keep their possessions. In other words, Acts 2:44 is describing a supererogatory work:
Acts Of Apostles 2:44
And all they that believed, were together, and had all things common.
Did they have to, to be Christians? No, it is just that all who were were doing this supererogatory work.
The Acts Of The Apostles 5: But a certain man named Ananias, with Saphira his wife, sold a piece of land,  And by fraud kept back part of the price of the land, his wife being privy thereunto: and bringing a certain part of it, laid it at the feet of the apostles.  But Peter said: Ananias, why hath Satan tempted thy heart, that thou shouldst lie to the Holy Ghost, and by fraud keep part of the price of the land?  Whilst it remained, did it not remain to thee? and after it was sold, was it not in thy power? Why hast thou conceived this thing in thy heart? Thou hast not lied to men, but to God.  And Ananias hearing these words, fell down, and gave up the ghost. And there came great fear upon all that heard it.
 Whilst it remained, did it not remain to thee? and after it was sold, was it not in thy power?
Having all things in common was a supererogatory work.
One which monks and friars and nuns and sisters were doing in England up to the Reformation.
And which Anglican and Royal Civil and Ecclesiastic Establishments ruthlessly sacked.
It is like sacking the first Church of Jerusalem. If this continued up to when Jerusalem Church fled to Pella, Henry VIII and Elisabeth and Edward VI between them (or rather his adult counsellors acting in his name, he died a boy) can be compared to Titus coming to sack Jerusalem.
Hans Georg Lundahl
Monday after St Joseph's Day
and Third Lord's Day in Lent