Matthew 20:23
He said to them: you will drink my cup, but to sit at my right hand and at my left is not mine to grant, but it is for those for whom it has been prepared by my Father. The confirmation that James and John will drink the cup (James martyred in Acts 12:2; John exiled to Patmos in Revelation 1:9) paired with the withholding of the status-grant: the positions are the Father's to assign, not the Son's to grant on request. The preparation language communicates the sovereign arrangement of the kingdom's final structure.