Scripture warns us not to be deceived (1 Cor. 6:9; 15:33). We can be deceived in many ways, but one of the major sources of deception is self. We find ways to avoid facing unpleasant truth and rationalize away personal guilt.
It is foolish to try to deceive ourselves. Galatians 6:7-9 touches on some common illusions among those who profess to be Christians. Sadly, those who try to deceive themselves and others by these things somehow think that God will likewise be deceived by them.
To mock is "to turn up the nose at, sneer at, treat with contempt, is used in the Passive Voice ... does not mean that men do not mock Him; the Apostle vividly contrasts the essential difference between God and man. It is impossible to impose upon Him who discerns the thoughts and intents of the heart" (W.E. Vine, Expository Dictionary of New Testament Words, p. 760).
God is not mocked in that His law cannot be ignored without punishment (Rom. 2:6-9). Adam and Eve tried it to their sorrow (Gen. 2:15-17; 3:6, 24). Ananias and Sapphira tried it to their death (Acts 5:1-11).
God is not mocked in that He cannot be deceived (Heb. 4:12-13). Achan concealed his sin from others but God was not mocked (Josh. 7). Gehazi, Elisha's servant, tried to gain a personal profit by lying but God was not mocked (2 Kings 5:20-27). Jonah tried to run from Him but God would not be mocked.
If one sows to the spirit, he has real hope of eternal life (2 Tim. 4:6-8). If one is sowing to the flesh, he had better be ready to reap corruption (Rom. 3:8; 6:23). One cannot neglect God's law without consequences (Heb. 2:2-3). One cannot sow the "works of the flesh" and reap heaven (Gal. 5:17-21). One cannot engage in such things as "adultery, fornication, uncleanness, lewdness, idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies, envy, murders, drunkenness, revelries, and the like" because "those who practice such things will not inherit the kingdom of God." One cannot sow "wild oats" and expect to reap that which is good.
As a matter of fact, we must look primarily beyond the present for reward. Paul said, "For I consider that the sufferings of this present time are not worthy to be compared with the glory which shall be revealed in us" (Rom. 8:18). He added, "For our light affliction, which is but for a moment, is working for us a far more exceeding and eternal weight of glory" (1 Cor. 4:17). One should never mistake God's present tolerance for a full harvest. Some were erroneously thinking that way in New Testament times. The apostle Peter corrected them by saying, "The Lord is not slack concerning His promise, as some count slackness, but is longsuffering toward us, not willing that any should perish but that all should come to repentance. But the day of the Lord will come as a thief in the night, in which the heavens will pass away with a great noise, and the elements will melt with fervent heat; both the earth and the works that are in it will be burned up" (2 Pet. 3:9-10). The young may escape the wrath of their parents, the law and society but they will not escape God's judgment. The worldly may think they have "gotten away with sin" if they receive no immediate penalty or if their sin is condoned by brethren -- but such is not the case.
All of us must realize that God will not be mocked -- neither in this life nor in eternity. He is not fooled by our clever deceptions. We will reap what we sow. Therefore, we must obey God.