In the context of these events and the language used, the reference for “those whom thou hast given me out of the world” in this case is the twelve. It is they who have become purified. In the sequencing of events, it would appear that this purification was a preliminary to becoming one with Jesus and the Father.
The sequencing of events suggests a building up of actions and blessings that culminate in the desired goal of having the twelve be “in him” and Jesus was “in” the Father. The last “action” is that Jesus “did smile upon them.” This would appear to be passive. It may have been some unheard or unstated action. Clearly it was a benediction upon the faith for the twelve, and after this “smiling” Jesus prays unspeakable things. This suggests that the event of true oneness happened at this point, and as with the earlier stages in this transformation, Jesus would then turn to give thanks to his Father that the events had happened as Jesus had prayed for.
This is not a state that is recorded for any other men, though it would not be surprising if it had also happened to the Old World twelve after Christ’s resurrection. Nevertheless, something of this experience is unusual, as Jesus declares that something has happened that no others have experienced (verse 36).