1 Corinthians 12:3 (NKJV) Therefore I make known to you that no one speaking by the Spirit of God calls Jesus accursed, and no one can say that Jesus is Lord except by the Holy Spirit.
What this means, in the context of all NT Scripture, is that no one can call Jesus their Lord whom they now listen to and follow, living by His Spirit, except by the Holy Spirit.
I say this, because many do, and will, say Jesus is Lord, but they do not mean it in the way the New Testament teaches.
For instance, in the following Scriptures, we cannot say that all these people who called Jesus "Lord" had the Holy Spirit:
Philippians 2:9-11 (WEB) 9 Therefore God also highly exalted him, and gave to him the name which is above every name, 10 that at the name of Jesus every knee should bow, of those in heaven, those on earth, and those under the earth, 11 and that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father.
Matthew 7:21-23 (WEB) 21 “Not everyone who says to me, ‘Lord, Lord,’ will enter into the Kingdom of Heaven, but he who does the will of my Father who is in heaven.
Matthew 25:11-12 (WEB) 11 Afterward the other virgins also came, saying, ‘Lord, Lord, open to us. 12 But he answered, ‘Most certainly I tell you, I don’t know you.’
Matthew 25:41 (WEB) 41 Then he will say also to those on the left hand, ‘Depart from me, you cursed, into the eternal fire which is prepared for the devil and his angels … 44 Then they will also answer, saying, ‘Lord, when did we see you hungry, or thirsty, or a stranger, or naked, or sick, or in prison, and didn’t help you?’
Luke 6:46 (WEB) 46 Why do you call me, ‘Lord, Lord,’ and don’t do the things which I say?
Luke 9:61-62 (WEB) 61 Another also said, “I want to follow you, Lord, but first allow me to say good-bye to those who are at my house.” 62 But Jesus said to him, “No one, having put his hand to the plow and looking back, is fit for God’s Kingdom.”
Luke 13:25 (WEB) 25 When once the master of the house has risen up, and has shut the door, and you begin to stand outside and to knock at the door, saying, ‘Lord, Lord, open to us!’ then he will answer and tell you, ‘I don’t know you or where you come from.’
In addition, before the Spirit was sent to believers to indwell them, many did believe in Jesus and called Jesus, "Lord," especially those who asked Jesus to heal them. Therefore, they called Jesus, "Lord, and they believed in him before ever being indwelt by the Spirit.
The Spirit was sent to indwell believers after the New Covenant was established - after Christ's death and resurrection, and after he was glorified.
John 7:37-39 (WEB) 37 Now on the last and greatest day of the feast, Jesus stood and cried out, “If anyone is thirsty, let him come to me and drink! 38 He who believes in me, as the Scripture has said, from within him will flow rivers of living water.” 39 But he said this about the Spirit, which those believing in him were to receive. For the Holy Spirit was not yet given, because Jesus wasn’t yet glorified.
John 16:7 Unless I go away, the Advocate will not come to you; but if I go, I will send him to you.
John 14:17 KJV: Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he [the Spirit] dwelleth {{{with}}} you, and shall be {{{in}}} you.
As you can see, not even the Disciples were indwelt by the Holy Spirit - not until Lord Jesus was glorified, and which began on the Day of Pentecost; and yet, the Disciples also called Jesus, "Lord."
