How do you define the humanism in Voltaire's Candide?

Humanism puts humans and their individual worth and dignity at the center of life, often rejecting religion or subordinating it in favor of reason. Humanism encourages people to cultivate their gifts and realize their potential.
At the end of Candide, Voltaire both depicts and defines his notion of humanism. Candide, Martin, and Pangloss experience it in the example of the old Turkish man. They, along with others, have been riveted over the strangulation of three important men in Constantinople and the impaling of some of the men's friends. But when, back in the countryside, they ask the "handsome" old man about it as he is taking the air in his doorway under an orange bough, he says he pays no attention to public affairs. Instead, he states:

I am contented with sending thither the produce of my garden, which I cultivate with my own hands.

He invites the men in. They are given homemade sherbet flavored with lemon, pineapple, orange, and pistachio nut, as well as good coffee. The man's two daughters perfume the visitors' beards.
Candide is so impressed by this generous bounty that he speculates that the man must have a "vast" estate. The man replies that he has, in fact, only twenty acres, which he and his daughters cultivate. The man notes:

our labor keeps off from us three great evils— idleness, vice, and want.

Candide is so impressed that he decides the man has chosen a better life than the six kings with whom he recently dined. Pangloss agrees, referring to the garden of Eden as a model.
Following the Turkish man's example, Candide, Pangloss, and their household settle on a similar small plot of ground, where they each keep busy and cultivate their gifts:

Cunegund ... became an excellent hand at pastrywork: Pacquette embroidered; the old woman had the care of the linen. There was none, down to Brother Giroflee, but did some service; he was a very good carpenter, and became an honest man.

This vision of everyone living a quiet but productive life illustrates Voltaire's humanist ideal. Voltaire defines humanism as cultivating one's garden, by which he means not necessarily a literal garden, but whatever your individual talent might be. Even though Pangloss continues to adhere to his optimistic philosophy, stating that they wouldn't have come to this peaceful place if they had not experienced all their sufferings, Candide gets the final, humanistic, word:

"Excellently observed," answered Candide; "but let us cultivate our garden."