It is not hard to find instances of the father in The Swiss Family Robinson giving advice to his children. He does so in almost every chapter. Usually these bits of advice are short and are offered in response to some crisis or decision that the family faces, or to some misbehavior on the part of his boys. But in chapter 16, "The First Sunday," the advice is much longer. For his Sunday "sermon," the father creates a long cautionary parable and then applies it directly to each of his sons.
Here are some examples of bits of brief advice given in the moment.
In Chapter 1, "Storm at Sea," when the family think they are facing death, the father encourages his boys, "God can save us if he will. To him nothing is impossible; but if he thinks it good to call us to him [i.e. that we die], let us not murmur [complain]: we shall not be separated [but shall be together in Heaven]."
In Chapter 2, "Marooned," the family has survived the first night on the ship but now face the daunting question of how they can save themselves. The father reminds them that God "has protected us till now, and will now extend a saving arm to us, if we do not give way to complaint and despair. Let all hands set to work. Remember that excellent maxim, 'God helps those who helps themselves.'"
In Chapter 4, "Safe and Sound," the oldest son, Fritz, becomes very angry with the family's dogs when they eat a wild pig that he has hunted. He beats them severely with his gun until the family can get him calmed down. Once his fit of rage has passed, the father "reproach[es] him seriously for his violence.
'Uncontrolled anger,' I said, 'leads to every crime. Remember Cain, who killed his brother in a fit of passion.'
'Oh, father!' said he, in a voice of terror."
These are just a few of many examples of advice the father gives whenever the occasion arises. As we can see from the third example, his advice is not an idle hobby but could be a matter of life and death for the family.
Now to the father's sermon in Chapter 16. The father tells an adventure story, sure to appeal to boys, of a king (who, in context, is obviously God) who sends some colonists to a deserted island equipped with seeds and a command to cultivate the island until he sends for them. The island is called Earthly Abode. Colonists are fetched from it by a ship called The Grave, and are brought back either to the Heavenly City or to the salt mines, according to how well they follow the king's instructions while on the island.
This is really brilliant. A tale of colonists on a deserted island is not only hugely relevant to the family's situation, but it brings out how their situation is like a microcosm of all of life on Earth, according to the father's Christian worldview. It also helps them re-frame their being marooned on an island as not just an unfortunate struggle for survival, but a sacred task that has been given to them.
But the father is not finished. After telling about the various ways in which the colonists in his parable neglected their duties, he goes on to apply these pointedly to his sons:
'You, Fritz, should take warning from the people who planted wild fruit and wished to make them pass for good fruit. Such are those who are proud of natural virtues ... such as bodily strength or physical courage, and place these above the qualities which are only attained by labor and patience.
'You Ernest, must remember the subjects who laid out their lands in flowery gardens, like those who seek the pleasures of life, rather than the duties. And you, my thoughtless Jack, and little Francis, think of the fate of those who left their land untilled, or heedlessly sowed tares for wheat. These are God's people who neither study nor reflect; who cast to the winds all instruction, and leave room in their minds for evil.'
He then wraps up with a final exhortation, which could serve as his motto in the book:
'Then let us all be, like the good laborers of the parable, constantly cultivating our ground, that when Death comes for us, we may willingly follow him to the feet of the Great King, to hear these blessed words: "Good and faithful servants! enter into the joy of your Lord!"'