1 Timothy 2:4
Who will have all men to be saved, and to come unto the knowledge of the truth.
Note 9 at 1Ti 2:4: God wills that all be saved (2Pe 3:9). Yet, not all are saved, and Scripture reveals that this will not happen (Mt 7:13-14). Therefore, what God wills doesn't always come to pass. Why? It's because of man's free will.
The Lord wills for everyone to be saved, but He gives people a choice. God doesn't make that choice for them, and the devil cannot force people into going to hell. It's their choice (De 30:19). Those who preach that God sovereignly predestines some to salvation and others to damnation totally miss this point (see note 2 at Ro 8:29).
Note 10 at 1Ti 2:4: In context, the "all men" that Paul was referring to were "kings, and for all that are in authority" (1Ti 2:2). Therefore, in Paul's day, this referred to Nero and many ungodly sub-rulers whom Paul stood before. The Lord hadn't written them off. He wanted them to be saved too.
The Lord arranged for His most powerful expositor of the Gospel to appear before Felix (see note 2 at Ac 23:24), Festus (see note 9 at Ac 24:27), King Agrippa II (see note 1 at Ac 25:13), centurion Julius (see note 4 at Ac 27:1), Publius (see note 1 at Ac 28:7), and even Caesar himself (Ac 25:11-12).
There is no account that any of these rulers ever repented and came to a saving faith in the Lord, but the Lord did arrange for them to hear the Gospel. It is often the tendency of believers to think that some people are too far gone to even bother witnessing to. That is not the example we see in Scripture, and it is not what Paul was advocating in these verses.
Note 11 at 1Ti 2:4: Notice that it is not only God's will for all to be saved, but He also wants all to come unto the knowledge of the truth. There is more to relationship with the Lord than just being saved. Believers need to renew their minds through the truth of God's Word, so that the salvation that is inside them manifests on the outside.