To enter into God's kingdom requires being chosen by God and following Jesus perfect example, being "born again" from "water and spirit".(John 3:3, 5) The apostle Paul wrote to the Thessalonians, that "because of your endurance and faith in all your persecutions and the tribulations that you are bearing...(that)...this is a proof of the righteous judgment of God, leading to your being counted worthy of the kingdom of God, for which you are indeed suffering."(1 Thess 1:4, 5)
Hence, those selected by God for the "heavenly calling" (Heb 3:1) must continue to measure up to "being counted worthy of the kingdom of God". What are the requirements ? Jesus told his apostles: "I am the true vine, and my Father is the cultivator. Every branch in me not bearing fruit he takes away, and every one bearing fruit he cleans, that it may bear more fruit."(John 15:1, 2) Hence, one must bear "fruit" and allow themselves to be cleansed by God.
What are some of the "fruit" ? Jesus continued, telling his apostles: "These things I command you, that you love one another. If the world hates you, you know that it has hated me before it hated you. If you were part of the world, the world would be fond of what is its own. Now because you are no part of the world, but I have chosen you out of the world, on this account the world hates you. Bear in mind the word I said to you, A slave is not greater than his master. If they have persecuted me, they will persecute you also; if they have observed my word, they will observe yours also."(John 15:17-19)
What does it mean to "love one another" and be "no part of the world" ? To "love one another" means that genuine love is shown for people of all nationalities, by having beaten "their swords into plowshares and their spears into pruning shears" so that "nation will not lift up sword against nation, neither will they learn war anymore."(Isa 2:4)
To be "no part of the world" means that a person will not involve himself in one aspect of the "world", the political elements, either directly or tacitly, for this would disqualify anyone from "being counted worthy of the kingdom of God." By involving oneself in the politics of this "world", would show that these are following the "god of this system of things", Satan the Devil.(2 Cor 4:4)
On the other hand, those who have followed in Jesus footsteps (1 Pet 2:21) and remained politically neutral as Jesus was, and as he stated, will be persecuted. About 1 1/2 years earlier, Jesus had told his apostles that "you will be objects of hatred by all people on account of my name; but he that has endured to the end is the one that will be saved."(Matt 10:22)
Thus, those "being counted worthy of the kingdom of God" must have endurance down to the end, either of their life (Rev 2:10) or to the "conclusion of the system of things".(Matt 24:3) These must be bearing witness about God's Kingdom, for Revelation 12:17 says that "the dragon (Satan) grew wrathful at the woman, and went off to wage war with the remaining ones of her seed, who observe the commandments of God and have the work of bearing witness to Jesus" as king of God's kingdom.(Matt 24:14)
In order for those selected by God for the purpose of becoming "a kingdom and priests to our God" (Rev 5:10), these have to allow themselves to be cleansed of any tainting of false religion, greedy commerce, or of the political arena, to "quit touching the unclean thing... and I (God) will take you in" (2 Cor 6:17), showing godly love. These are then measuring up to the requirements for "being counted worthy of the kingdom of God."