In light of the modern corrupt "Christian" church and corrupt society full of "Christians" whom Christ will not recognize as His, it is no wonder that Christ queried, "When the Son of man returneth shall He find faith yet upon the earth?"
Faith is not a "free floating" phenomenon. Faith is the dynamic Presence of the Holy Spirit within God's elect, Who leads them into Truth and empowers them to obey God and thus be pleasing to Him. Without faith it is impossible to please God, because faith without works (fruit) is not faith. It is a humanistic spiritualism, a nice idea, a superstition. Faith cometh by the Word of God. Faith is the working knowledge of the facts of God's Word—Doctrine, Commands. Those devoid of that are devoid of God. "Every tree is known by its fruit." "Be ye doers of the Word, not hearers only, deceiving your own selves." Works do not contribute to faith; that is the wrong perspective, confusing "cause and effect". True faith produces the works that God fore-ordained that we should walk therein. Faith that does not produce what God sent it forth to produce, was not sent by God and is "counterfeit faith"—a humanistic delusion; a carnal pesudo-spiritual substitute for true faith (and thus it is Anti-Christ and that is why Christ will reject it; even as God rejected Cain and his sacrifice—it was not within Cain to offer that which God commanded; Cain offered instead a bloodless sacrifice, something that Cain imagined was better, or all that he was willing to offer).
Christ also revealed that many "Christians" who thought that they were doing "wonderful works" in "His Name" shall hear, "depart from Me, yet that work iniquity (lawlessness); I never knew you". That's quite a shocker. This is not spoken to people who do not even consider themselves Christians, but to Christians who even thought that they were serving God and doing wonderful things... and they will hear that they are immoral... iniquitous, lawless--violators of the morality that God commanded. Even as Christ said, those who are not with Me are against Me and those who gather not with Me (presumably, the lost sheep) SCATTER abroad. If we do not have the EXACT same agenda, plan, mission that Christ commanded, "as the Father sent Me so send I you... go only to the lost sheep of the House of Israel... then go into all the world (to Israel whither God had scattered them)..." Modern pseudo-Christianity reject doctrine, rejects God's Law (anti-intellectually thinking God abolished it when Christ said He did not), they cast down all the moral boundaries that God established, wallow in filth thinking that it is righteousness and that God will be so happy with them, with the dogs breeding on top of the table with the master's children. God doesn't change. Morality does not change. Those who think so are under profound delusion and do not know God.
that is even more damning than "I know not who you are". It used to be, in moral Christendom, parents raised their children to be moral and godly and follow in the father's footsteps. It was common for someone to ask, upon meeting you (if your last name was a common name), "Who's your father?" If one knew the father and the father was a righteous, fair, honest man, then it was most likely so were the children.
Sadly, those times have come and gone.
[Modernly, a different saying, "Who's your daddy?" has entirely replaced the meaning of "Who's your father?"]
Unless God's people return to what God commanded, as in Isaiah 58, if we obey out of sincerity and purity of heart; not merely going through the motions. If we obey in the letter and in the spirit...
9Then shalt thou call, and the LORD shall answer; thou shalt cry, and he shall say, Here I am. If thou take away from the midst of thee the yoke, the putting forth of the finger, and speaking vanity;
10And if thou draw out thy soul to the hungry, and satisfy the afflicted soul; then shall thy light rise in obscurity, and thy darkness be as the noonday:
11And the LORD shall guide thee continually, and satisfy thy soul in drought, and make fat thy bones: and thou shalt be like a watered garden, and like a spring of water, whose waters fail not.
12And they that shall be of thee shall build the old waste places: thou shalt raise up the foundations of many generations; and thou shalt be called, The Repairer of the breach, The Restorer of paths to dwell in.
13If thou turn away thy foot from the sabbath, from doing thy pleasure on my holy day; and call the sabbath a delight, the holy of the LORD, honourable; and shalt honour him, not doing thine own ways, nor finding thine own pleasure, nor speaking thine own words:
14Then shalt thou delight thyself in the LORD; and I will cause thee to ride upon the high places of the earth, and feed thee with the heritage of Jacob thy father: for the mouth of the LORD hath spoken it."
(my own emphatic paraphrase) (Isaiah 58:12)