How do we know Jesus's words about preparing a place are true?

The truth of Jesus's promise that He prepares a place for believers is substantiated by His sacrificial death on the cross and subsequent resurrection. In John 16:20-22, Jesus illustrates that though His disciples will grieve at His departure, their sorrow will be turned into joy when they see Him again. The completion of this promise, where believers are ultimately welcomed into the presence of God, is realized through the redemptive work Jesus accomplished on the cross, cemented by His resurrection, as outlined in Hebrews 10:14.