Here is the rest of the sermon by St. Francis de Sales on fasting; Part I is here.
The second condition is never to fast through vanity but always through humility. If our fast is not performed with humility, it will not be pleasing to God… St. Paul in the epistle that he wrote to the Corinthians [1 Cot: 13]…declared the conditions necessary for disposing ourselves to fast well during Lent. He says this to us: Lent is approaching. Prepare yourselves to fast with charity, for if your fast is performed without it, it will be vain and useless, since fasting, like all other good works, is not pleasing to God unless it is done in charity and through charity. When you discipline yourself, when you say long prayers, if you have not charity, all that is nothing. Even though you should work miracles, if you have not charity, they will not profit you at all. Indeed, even if you should suffer martyrdom without charity, your martyrdom is worth nothing and would not be meritorious in the eyes of the Divine Majesty. For all works, small or great, however good they may be in themselves, are of no value and profit us nothing if they are not done in charity and through charity.
I say the same now: if your fast is without humility, it is worth nothing and cannot be pleasing to the Lord…
But what is it to fast through humility? It is never to fast through vanity. Now how can one fast through vanity? …To fast through vanity is to fast through self-will, since this self-will is not without vanity, or at least not without a temptation to vanity. And what does it mean to fast through self-will? It is to fast as one wishes and not as others wish; to fast in the manner which pleases us, and not as we are ordered or counseled. You will find some who wish to fast more than is necessary, and others who do not wish to fast as much as is necessary. What causes that except vanity and self-will? All that proceeds from ourselves seems better to us, and is much more pleasant and easy for us than what is enjoined on us by another, even though the latter is more useful and proper for our perfection. This is natural to us and is born from the great love we have for ourselves.
Let each one of us examine our conscience and we will find that all that comes from ourselves, from our own judgment, choice and election, is esteemed and loved far better than that which comes from another. We take a certain complacency in it that makes the most arduous and difficult things easy for us, and this complacency is almost always vanity. You will find those who wish to fast every Saturday of the year, but not during Lent. They wish to fast in honor of Our Lady and not in honor of Our Lord. As if Our Lord and Our Lady did not consider the honor given to the one as given to the other, and as if in honoring the Son by fasting done for His intention, one did not please the Mother, or that in honoring the Virgin one did not please the Savior! What folly! But see how human it is: because the fast that these persons impose on themselves on Saturday in honor of our glorious Mistress comes from their own will and choice, it seems to them that it should be more holy and that it should bring them to a much greater perfection than the fast of Lent, which is commanded. Such people do not fast as they ought but as they want.
There are others who desire to fast more than they should… On this matter the great Apostle complains [Rom. 14:1-6], saying that we find ourselves confronted by two groups of people. Some do not wish to fast as much as they ought, and cannot be satisfied with the food permitted (this is what many worldly people still do today who allege a thousand reasons on this subject... The others, says St. Paul, wish to fast more than is necessary. It is with these that we have more trouble. We can easily and clearly show the first that they contravene the law of God, and that in not fasting as much as they should, while able to do it, they transgress the commandments of the Lord. But we have more difficulty with the weak and infirm who are not strong enough for fasting. They will not listen to reason, nor can they be persuaded that they are not bound by it [the law of fasting], and despite all our reasons they insist on fasting more than is required, not wishing to use the food we order them. These people do not fast through humility, but through vanity. They do not recognize that, being weak and infirm, they would do much more for God in not fasting through the command of another and using the food ordered them, than in wishing to abstain through self-will. For although, on account of their weakness, their mouth cannot abstain, they should make the other senses of the body fast, as well as the passions and powers of the soul.
You are not, says Our Lord, to look gloomy and melancholic like the hypocrites do when they fast in order to be praised by men and esteemed as great abstainers.{3} [Matt.6:16-18]. But let your fasting be done in secret; therefore, wash your face, anoint your head, and your heavenly Father who sees what is hidden in your heart will reward you well. Our Divine Master did not mean by this that we ought to have no care about the edification of the neighbor. Oh, no, for St. Paul says [Phil. 4:5]: Let your modesty be known to all. Those who fast during the holy season of Lent ought not to conceal it, since the Church orders this fast and wishes that everyone should know that we are observing it. We must not, then, deny this to those who expect it of us for their edification, since we are obliged to remove every cause of scandal to our brothers. But when Our Lord said: Fast in secret, He wanted us to understand: do not do it to be seen or esteemed by creatures; do not do your works for the eyes of men. Be careful to edify them well, but not in order that they might esteem you as holy and virtuous. Do not be like the hypocrites. Do not try to appear better than others in practicing more fasting and penances than they.
…Accomplish your good works in secret and not for the eyes of others. Do not act like the spider, which represents the proud; but imitate the bee, which is the symbol of the humble soul. The spider spins its web where everyone can see it, and never in secret. It spins in orchards, going from tree to tree, in houses, on windows, on floors -- in short, before the eyes of all. In this it resembles the vain and hypocritical who do everything to be seen and admired by others. Their works are in fact only spiders' webs, fit to be cast into the fires of Hell. But the bees are wiser and more prudent, for they prepare their honey in the hive where no one can see them. Besides that, they build little cells where they continue their work in secret. This represents very well the humble soul, who is always withdrawn within herself, without seeking any glory or praise for her actions. Rather, she keeps her intention hidden, being content that God sees and knows what she does.
…Do not allow your fast to resemble that of hypocrites, who wear melancholy faces and who consider holy only those who are emaciated. What folly! As if holiness consisted in being thin! Certainly St. Thomas Aquinas was not thin; he was very stout. And yet he was holy. In the same way there are many others who, though not thin, nevertheless fail not to be very austere and excellent servants of God. But the world, which regards only the exterior, considers only those holy who are pale and wasted. Consider a little this human spirit: it takes account only of appearances and, being vain, does its works to be seen by others. Our Lord tells you not to do as they do but to let your fast be done in secret, only for the eyes of your heavenly Father, and He will see you and reward you.
The third condition necessary for fasting well is to look to God and to do everything to please Him, withdrawing within ourselves in imitation of a great saint, St. Gregory the Great, who withdrew into a secret and out-of-the-way place where he remained for some time without anyone knowing where he was, being content that the Lord and His angels knew it.
…Cassian says: What will it profit you to do what you are doing for the eyes of creatures? Nothing but vanity and complacency, which are good for Hell alone. But if you keep your fast and do all your works to please God alone, you will labor for eternity, without delighting in yourself or caring whether you are seen by others or not, since what you do is not done for them, nor do you await your recompense from them. We must keep our fast with humility and truth, and not with lying and hypocrisy -- that is, we must fast for God and to please Him alone.
…This is all that I had to tell you regarding fasting and what must be observed in order to fast well. The first thing is that your fast should be entire and universal; that is, that you should make all the members of your body and the powers of your soul fast…If you do that, your fast will be universal, interior and exterior, for you will mortify both your body and your spirit. The second condition is that you do not observe your fast or perform your works for the eyes of others. And the third is that you do all your actions, and consequently your fasting, to please God alone, to whom be honor and glory forever and ever.
In the name of the Father, and of the Son, and of the Holy Spirit. Amen.