The watchmen are they who declare the message of salvation, those who are set to watch and raise the warning voice (see Ezekiel 33:6-7). Abinadi is a perfect example of a watchman lifting that voice of warning.
“Thy Watchmen Shall Lift Up the Voice”
There is no more beautiful sight to those in bondage than he who comes to liberate them. Isaiah’s description is of the missionaries who go forth fearlessly declaring the message of the restored gospel. (See commentary on Mosiah 15:14-19; 3 Nephi 20:40.)