In the Old Testament, God has many, many warnings for people, and He frequently began His warning with the word "beware!" "Beware" means to be warned, to be wary, or to be on guard. Warnings, at least from God, are motivated out of concern for the well being of the ones being warned. The Old Testament uses "beware" twelve times employing a variety of messengers, and addressing individuals, societies, or humanity in general. They are: Beware of endangering my family (Gen. 24:8). Beware of provoking My angel (Ex. 23:21). Beware of forgetting what the Lord has done for you (Deut. 6:12). Beware of falling into sin (Deut. 8:11). Beware of thinking how you can withhold help for the brethren (Deut. 15:9). Beware of wine and strong drink (Jud. 13:4). Beware of failing to obey My instructions (Jud. 13:13). Beware that you do not harm God's anointed (2 Sam. 18:12). Beware of going where you are not welcome (2 Kg. 6:9). Beware of committing a sin unto death (Job 36:18). Beware of copying the behavior of those being disciplined (Prov. 19:25). Beware of listening to those whose counsel is opposed to the teachings of God (Isa. 36:18).
In the New Testament, God also has many warnings for those He loves. The word "beware" is used fourteen times, but because the Gospels duplicate the record of them, there are actually only eight. They are: Beware of false prophets (Matt. 7:15). Beware of men who wish to do you harm (Matt. 10:17). Beware of the leaven (hypocrisy) of the Pharisees, Sadducees, and the scribes (Matt. 16:6, 11, 12; Mk. 8:15; 12:38; Lk. 12:1; 20:46). Beware of covetousness (Lk. 12:15). Beware of rejecting the Gospel of Jesus Christ (Acts 13:40). Beware of dogs, evil workers, and of the concision (Phil. 3:2). This may very well be Paul using three terms to describe the same people. Paul's major opposition to the preaching of salvation by grace apart from works, came from those claiming to be Jewish converts to Christ. They did everything they could to undermined his ministry (Nearly all of the Book of Galatians). The last two are: Beware of falling for human philosophy and empty lies (Col. 2:8). Beware of being led astray from sound doctrine (2 Pet. 3:17).
God holds those have knowledge of Him or light, to warn those who are lost. In the Old Testament, He uses the term "watchman" to describe those who He has appointed to warn others of danger. He gives us an ultimatum: I warn you not to fail to warn them (2 Chron. 19:10). The Lord is more specific in Ezekiel where He tells us that failure to warn others results in His judgment upon the "watchman" (Ezek. 3:17-21; 33:3-7). In a clear sense, He holds those who fail to warn others who are killed, guilty of murder. If He is that emphatic about warning those who are in danger of physical death, what do you suppose He thinks of those who fail to warn others resulting in the loss of their soul? If you love God, love those for whom He gave His Son! If you love God, share Him with others!
After all, even Satan warns his minions (Matt. 3:7; Lk. 3:7)!