Pope Francis cautioned against the false appearances of those who are proud or vain, saying that true holiness is found in the silent, everyday witness of the poor and humble.

"We should think about so much hidden holiness there is in the Church; Christians who remain in Jesus," the Pope told those present in the Vatican's Saint Martha guesthouse for his Dec. 4 daily Mass.

While there are there are some Christians who put on appearances, many others are true saints, he said, noting that they are not necessarily "canonized saints, but saints (who) put the love of Jesus into practice."

The Pope centered his reflections on the day's first reading from the prophet Isaiah, who speaks of the importance of founding oneself on the rock of the Lord, and foretells the destruction of the high and "lofty" cities, who will be trampled by the poor and needy.

When it comes to being a true Christian, the Pope said, we should not be "Christians in appearance," whose make-up comes off as soon as the rain begins.

"So many 'apparent Christians,' collapse at the first temptation (because) there is no substance there," so it's not enough to simply belong to a Catholic family, an association or to be a benefactor if we don't follow God's will.

However, there are also many who do follow God's will and put his love into practice every day, Pope Francis noted, pointing to those who are considered small but who offer their daily suffering to the Lord.

"Let us consider the sick who offer their sufferings for the Church, for others. Let us consider so many of the elderly who are alone, who pray and make offerings," he said, also recognizing the many families who work hard to raise children and who don't "strut about," but bear their problems with hope.

These people are "the saints of daily life," the Pope said. He also lauded the witness of the many parish priests who carry out their work with love, and without being seen.

Priests who work hard catechizing children, caring for the elderly and the sick, and preparing couples for marriage do the same thing every day, he said, but never get bored "because their foundation is the rock. It is Jesus, it this that gives holiness to the Church, it is this that gives hope!"

Even these hidden saints are still sinners, because we all are, he observed, saying that when a good Christian sometimes falls and commits a grave sin but is penitent and asks forgiveness, it is a good thing.

"Not confuse sin with virtue," the Pope said, explaining that it's good to "know well where virtue is, and where sin is, (but) these (people) are founded on rock, and the rock is Christ."

The proud and the vain are those who have built their house on sand, the Pope said, noting that as the prophet Isaiah said in the first reading, they will be "demolished" while the poor and those who consider themselves nothing in the sight of God will triumph.

He concluded his reflections by encouraging all present to use the time of Advent, in which we prepare for the coming of Jesus at Christmas, to place our foundation on the Lord, who is our rock and our hope.

"We are all sinners, we are weak, but if we place our hope in Him we can go forward. And this is the joy of a Christian: knowing that in Him there is hope, there is pardon, there is peace (and) there is joy."