5 for you are all sons of light and sons of day. We are not of night nor of darkness; 6 so then, let’s not sleep as others do, but let’s be alert and sober. 1 Thessalonians 5:5, NASB
The words “light” and “night” refer to either being in the truth or still being blind, not knowing the Lord Jesus Christ. It can also mean that a Christian could be living in sin or not busy doing God’s will and thus “asleep” spiritually. To be “sober”, we must not be deluded with sin and with the things of this life, but making sure we are in right standing with the Lord and doing good works.
We must have our minds filled with the Word of God and spreading the good news to bring as many to the kingdom of heaven as possible. Of course, convicting people of their sins is done solely by the Holy Spirit. Our part is to tell them what the Bible says about Jesus. God will do the rest.