Rom 10:13-15, 1 Cor 9:16
In the Old Testament, God appointed Ezekiel as a watchman for the people of Israel to spread the gospel. (Ezekiel 3:17-21)
Ezekiel 3:17 Son of man, I have made thee a watchman unto the house of Israel: therefore hear the word at my mouth, and give them warning from me. 18 When I say unto the wicked, Thou shalt surely die; and thou givest him not warning, nor speakest to warn the wicked from his wicked way, to save his life; the same wicked man shall die in his iniquity; but his blood will I require at thine hand. 19 Yet if thou warn the wicked, and he turn not from his wickedness, nor from his wicked way, he shall die in his iniquity; but thou hast delivered thy soul. 20 Again, When a righteous man doth turn from his righteousness, and commit iniquity, and I lay a stumbling-block before him, he shall die: because thou hast not given him warning, he shall die in his sin, and his righteousness which he hath done shall not be remembered; but his blood will I require at thine hand. 21 Nevertheless if thou warn the righteous man, that the righteous sin not, and he doth not sin, he shall surely live, because he is warned; also thou hast delivered thy soul.
God has established us as watchmen who preach the gospel of salvation. If we do not preach the gospel of salvation, people cannot hear the gospel of salvation. (Romans 10:13-15)
Romans 10:13 For whosoever shall call upon the name of the Lord shall be saved. 14 How then shall they call on him in whom they have not believed? and how shall they believe in him of whom they have not heard? and how shall they hear without a preacher? 15 And how shall they preach, except they be sent? as it is written, How beautiful are the feet of them that preach the gospel of peace, and bring glad tidings of good things!
Woe to us if we do not preach the gospel. (1 Corinthians 9:16)
1 Corinthians 9:16 For though I preach the gospel, I have nothing to glory of: for necessity is laid upon me; yea, woe is unto me, if I preach not the gospel!