Sometimes it is a solemn duty before God to warn people, Eze 3:20. See also Pr 29:1.

1. Warnings of Example, Jude 1:6,7,17-19.

2. Warnings of Instruction, concerning,

• the uncertainty of life, Jas 4:13-14;
• offending the living God, Rom 2:8-9;
• forsaking Christ, Heb 2:1-4;
• turning away from our only hope, Acts 4:12

3. Warnings of Experience,

• that the experience of sin is bitter, Rom 7:24
• that the enjoyments of salvation are sweet, 2 Thess 2:16-17
• that warning, in order to do us good, must be
  • heard, 2 Tim 4:3-4,
  • believed, Gen 19:14;
  • obeyed, Mt 21:28-31,

(Richardson, in The Biblical Illustrator, adapted)