As to your first question, God will only allow so much evil and then He will judge it. In Genesis chapter 15 God was telling Abraham, who was living in the land of Canaan, how His “descendants will be strangers in a land that is not theirs, and will serve them, and they will afflict them four hundred years” (verse 13). We know He was speaking of their bondage in the land of Egypt. He went on to say “And also the nation whom they serve I WILL JUDGE; afterward they shall come out with great possessions…. But in the fourth generation they shall return here, for THE INIQUITY OF THE AMORITES IS NOT YET FULL.” Here Abraham learned that God would judge Egypt and the Israelites would return to Canaan (the Promised Land), but that they wouldn’t be permitted to enter Canaan until the fourth generation BECAUSE “the iniquity of the Amorites (Canaanites) was not yet FULL.” This teaches us a truth about WHEN GOD JUDGES EVIL; He waits until “the cup of sin is FULL!” He allows men to go on sinning to a certain point and when He can no longer tolerate it (when “the cup of sin is FULL”), He judges them. God is holy and must judge sin and when “the time is ripe He will execute judgment in perfect accord with His holy character” (H. A. Ironside).

We see another clear example of this in Genesis 6:5-7, “Then the LORD saw that the WICKEDNESS of man was GREAT in the earth, and that every intent of the thoughts of his heart was only EVIL CONTINUALLY. And the LORD was sorry that He had made man on the earth, and He was grieved in His heart. So, the LORD said, ‘I will DESTROY MAN whom I have created from the face of the earth, both man and beast, creeping thing and birds of the air, for I am sorry that I have made them.’” These words clearly teach us that “the cup of sin was FULL” and God, who is holy, would have to “destroy man” on account of their evil hearts. We read on in verses 11-13, “The earth also was corrupt before God, and THE EARTH WAS FILLED WITH VIOLENCE. So, God looked upon the earth, and indeed it was corrupt; for all flesh has corrupted their way on the earth. And God said to Noah, ‘The end of all flesh has come before Me, for the earth is FILLED WITH VIOLENCE through them; and behold, I will destroy them with the earth.’”  Here again we see that “the cup of sin was FULL.” Men’s hearts were “evil continually” and “the earth was FILLED with violence.” God had no other choice but to wipe man off the face of the earth (except for Noah and his family) and He would use a flood to accomplish this.

In Acts 17:31 God has promised to judge the world again, “because He has appointed a day on which He will JUDGE THE WORLD IN RIGHTEOUSNESS by the Man whom He has ordained.” When will He do this? When “the cup of sin is FULL!” Jesus (the “Man” whom God has ordained) said in Matthew 24:37, “But as the days of Noah were, so also will the coming of the Son of Man be.” In other words, Jesus was teaching us that the conditions that existed in the days of Noah would be duplicated and then He would come again to execute God’s righteous judgment. Do we see those conditions today? Are men’s hearts “only EVIL CONTINUALLY” and is “the earth FILLED WITH VIOLENCE?” Any honest observer, who watches the daily news, would have to admit that we are indeed seeing these “signs of the times” and thus it may very well be that “the cup of sin is reaching the brim!” Yet until the cup is FULL (and only God knows exactly when that is) God “is longsuffering towards us, not willing that any should perish but that all should come to repentance” (2^nd Peter 3:9). God, in grace, is showing mercy to sinners by giving them time to “repent of their sins and to believe the gospel of Jesus Christ.” Jesus told the Jews in His day, “Repent, and believe in the gospel” (Mark 1:15). The Apostle Paul taught “publicly and in every house, testifying to both Jews and Greeks REPENTANCE towards God, and FAITH towards our Lord Jesus Christ” (Acts 17:20-21). If my reader has not yet “repented of his sins and believed on the Lord Jesus Christ for salvation,” I would plead with you to do so before “the cup of sin is full” and God’s judgment falls on this wicked, Christ-rejecting world.

You go on to ask, “How does a Christian keep his faith?” First of all, the believer in Christ must NOT be occupied with the evil in the world. In Romans 16:19 we are exhorted “to be wise in what is good, and simple concerning evil.” We should saturate our minds with what is GOOD and avoid being taken up with EVIL, whether it be FALSE DOCTRINE that evil men are teaching or WICKED BEHAVIOR (violence and corruption) all around us. We are told in Philippians 4:8, “Finally, brethren, whatever things are TRUE, whatever things are NOBLE, whatever things are JUST, whatever things are PURE, whatever things are LOVELY, whatever things are of GOOD REPORT, if there is any VIRTUE, and if there is anything PRAISEWORTHY—MEDITATE ON THESE THINGS.” If our minds are occupied with “what is GOOD,” we won’t be overwhelmed by “the EVIL in the world.”

Besides being taken up with what is GOOD, God’s “DIVINE POWER HAS GIVEN TO US ALL THINGS that pertain to life and godliness” (2^nd Peter 1:3). This means He has given to us all the RESOURCES we need to “keep the faith.” He has given us  1) a Divine Nature (2^nd Peter 1:4 and 1^st John 3:9), 2) the Holy Spirit (Acts 1:8; Galatians 5:16-17 and 1^st Corinthians 2:9-13), 3) the Word of God (Acts 20:32; 1^st Peter 2:2; Psalm 119:11 and John 17:14-17), 4) the Throne of Grace (Hebrews 4:14-16), 5) the Fellowship of Believers (Hebrews 10:24-25), 6) the Lord’s Coming as our “blessed hope” (Titus 2:13 and 1^st John 3:2-3), and last, but not least, 7) Christ in the Glory as an OBJECT for the Heart (Colossians 3:1-2 and 2^nd Corinthians 3:18. The Bible tells us that we “are KEPT BY THE POWER OF GOD THROUGH FAITH for salvation ready to be revealed in the last time” (1^st Peter 1:5) and it is through these “Divine Resources” that He keeps us!  (488.5)  (DO)