Philippians 1:23 (ESV)

23 I am hard pressed between the two. My desire is to depart and be with Christ, for that is far better.

It is a two-way street for Paul. He is pulled in both directions. On the one hand, he longs to die. He uses a different word here for dying. In shipping it means: to lift the anchor, and it is also used for a tent: to break down the tent. Perhaps Paul was thinking of the latter. In short, it means to depart. The departure for Paul is to be with Christ. To him, that is the best. He is already connected to Christ by faith in him. After death the bond with Christ changes, then he is really with Christ. Close to his Lord in a new, unprecedented way. The being with Christ begins immediately after death.

In another letter, he writes that the believers will always be with the Lord after Christ’s return (1 Thessalonians 4:17). That is not contrary to what Paul writes here. There the topic is: how will it be at the second coming of Christ? Will we meet again?

This concerns the question of what happens when we die (see also 1 Thessalonians 4:17). The answer to that is: we meet Christ (for texts in the OT, see also: Psalm 16:11 and Psalm 73:23–24; and in the NT: Luke 20:38, Luke 23:43 and John 11:25–26). Paul does not write: When I die, I go to heaven. That is true, but he does not say it that way. It is never said that way in the NT. The most important is being with Christ.