And Jesus answering saith unto them, Have faith in God. -Mark 11:22

Virtues without faith are whitewashed sins. Obedience without faith, if it is possible, is a gilded disobedience. Not to believe, nullifies everything. It is the fly in the ointment; it is the poison in the pot. Without faith, with all the virtues of purity, with all the benevolence of philanthropy, with all the kindness of disinterested sympathy, with all the talents of genius, with all the bravery of patriotism, and with all the decision of principle-“without faith it is impossible to please God.” Do you not see then, how bad unbelief is, because it prevents men from performing good works.

Faith fosters every virtue; unbelief murders every one. Thousands of prayers have been strangled in their infancy by unbelief. Unbelief has been guilty of infanticide; it has murdered many an infant petition; many a song of praise that would have swelled the chorus of the skies, has been stifled by an unbelieving murmur; many a noble enterprise conceived in the heart has been blighted ere it could come forth, by unbelief. Many a man would have been a missionary; would have stood and preached his Master’s gospel boldly; but he had unbelief. Once make a giant unbelieving, and he becomes a dwarf. Faith is the Samsonian lock of the Christian; cut it off, and you may put out his eyes-and he can do nothing. ~ C.H. Spurgeon

http://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0003.cfm