The "Oath of Allegiance" taken by all who choose to become naturalized citizens of the United States follows. Immediately after saying the oath one's citizenship is in effect.
"I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state or sovereignty of whom or which I have heretofore been a subject or citizen; that I will support and defend the Constitution and laws of the United States of America against all enemies, foreign and domestic; that I will bear arms on behalf of the United States when required by the law; that I will perform noncombatant service in the Armed Forces of the United States when required by the law; that I will perform work of national importance under civilian direction when required by the law; and that I take this obligation freely, without any mental reservation or purpose of evasion; so help me God."
As believers, we could say our citizenship in heaven is put into effect immediately after saying a similar oath ...
"I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state or sovereignty of whom or which I have heretofore been a subject or citizen; that I will follow the Lamb of God, Jesus Christ, without reservation; support and follow the values and virtues of the Kingdom of God as given in the Holy Scriptures; that I will bear witness to the truth; and that I take this obligation freely without any mental reservation or purpose of evasion; so help me God."