Revelation 14:9

then a third angel followed
The first angel brought the carrot (Rev. Rev. 14:6+), now the third brings the stick! Those who would not respond to God’s gracious offer of salvation are now warned of the eternal significance of worshiping the Beast and taking his mark. Unfortunately, many at the time of the end will follow in the well-worn pattern of those before them who continued to ignore God’s gracious warning:

However I have sent to you all My servants the prophets, rising early and sending them, saying, “Oh, do not do this abominable thing that I hate!” But they did not listen or incline their ear to turn from their wickedness, to burn no incense to other gods. So My fury and My anger were poured out and kindled in the cities of Judah and in the streets of Jerusalem; and they are wasted and desolate, as it is this day. (Jer. Jer. 44:4-6)

If anyone worships the beast
See commentary on Revelation 13:4. and his image
See commentary on Revelation 13:14 and Revelation 13:15.

and receives his mark on his forehead or on his hand
See commentary on Revelation 13:16.