When righteous people die, we have no reason to doubt but that they are saved. That is, they are heirs of the celestial kingdom. When the righteous (those true to their gospel covenants) pass from this life to the next, they “are received into a state of happiness, which is called paradise, a state of rest, a state of peace, where they shall rest from all their troubles and from all care, and sorrow” (Alma 40:12).
Since they have kept their second estate, the eternal promise is that they “shall have glory added upon their heads for ever and ever” (Abraham 3:26). Given, then, that there is no apostasy in paradise, all who obtain that station have the sure promise of celestial glory in the day of resurrection.