Church Fathers Commentary Luke 17:5-6

"And the apostles said unto the Lord, Increase our faith. And the Lord said, If ye had faith as a grain of mustard seed, ye would say unto this sycamine tree, Be thou rooted up, and be thou planted in the sea; and it would obey you." — Luke 17:5-6 (ASV)

Theophylact of Ohrid: When the disciples heard our Lord discussing certain difficult duties, such as poverty and avoiding offense, they pleaded with Him to increase their faith. They did this so that they might be able to embrace poverty—for nothing so prompts a life of poverty as faith and hope in the Lord—and through faith to guard against causing offense. Therefore, it is said, And the apostles said to the Lord, “Increase our faith.”

St. Gregory the Great: That is, that the faith which has already been received in its beginning might continue to increase more and more toward perfection.

St. Augustine of Hippo: We may indeed understand that they asked for an increase of that faith by which people believe in things they do not see. But it also signifies a faith in things, by which we believe not with words only, but with the things themselves present before us. And this will happen when the Wisdom of God, by whom all things were made, reveals Himself openly to His saints face to face.

Theophylact of Ohrid: But our Lord told them that they asked well and that they ought to believe steadfastly, since faith could do many things. Therefore, He continued, “If you had faith like a grain of mustard seed...” Two mighty acts are brought together in this same sentence: transplanting what is rooted in the earth, and planting it in the sea (for what is ever planted in the waves?). By these two things, He declares the power of faith.

St. John Chrysostom: He mentions the mustard seed because, though small in size, it is greater in power than all the others. He implies, then, that even the smallest amount of faith can do great things. But though the Apostles did not transplant the mulberry tree, do not accuse them, for our Lord did not say, “You shall transplant,” but, “You shall be able to transplant.” They did not do so because there was no need, since they performed even greater things. But someone will ask: How can Christ say that the smallest amount of faith can transplant a mulberry tree or a mountain, whereas Paul says that it is “all faith” that moves mountains? We must answer that the Apostle attributes the moving of mountains to “all faith,” not as if only the whole of faith could do this, but because this seemed a great thing to carnal men on account of the object’s vast size.

The Venerable Bede: Alternatively, our Lord here compares perfect faith to a grain of mustard seed because it is lowly in appearance but fervent in heart. Mystically, however, the mulberry tree (whose fruit and branches are a blood-red color) represents the Gospel of the cross. Through the faith of the Apostles, this Gospel was uprooted by the word of preaching from the Jewish nation—where it was kept, as it were, in its ancestral line—and was removed and planted in the sea of the Gentiles.

St. Ambrose of Milan: Alternatively, this is said because faith keeps out the unclean spirit, a meaning which the nature of the tree supports. For the fruit of the mulberry is at first white in the blossom; then, being formed from it, grows red and blackens as it ripens. The devil, too, having fallen by transgression from the white flower of his angelic nature and the bright beams of his power, becomes terrible in the black foulness of sin.

St. John Chrysostom: The mulberry tree may also be compared to the devil. For just as certain worms are fed by the leaves of the mulberry tree, so the devil, by the imaginations that proceed from him, is feeding for us a never-dying worm. But faith is able to pluck this mulberry tree out of our souls and plunge it into the deep.