And when he had taken leave of them, he went off to the mountain to pray.  Mark 6,46

Jesus, who came among his people, to be with them, to teach them and to heal them,
takes leave of them. 
He sends away the crowd and 
asks his disciples to proceed to the other side of the river.
It looks as if Jesus does not want anyone to be on this/his side. Strange.
Why so?
He has just done a miracle and that too amidst a crowd of 5000 people.
And his disciples had not understood the happenings. 
He leaves the people and goes on to the mountain to pray.
He could have prayed with the people.
 He has prayed with the people in the Synagogues…
 he has prayed in front of the people – before raising Lazarus from the tomb… 
and at other times.
But this times he goes alone to pray.
This could be a time for prayer of union, with the Father-
He and the Father alone.
Probably there is no reciting /saying of prayers in this type.
But a prayer of communion or mystical union !!!
But after the prayer he is back again with his disciples.
His prayer (of communion or mystical union) only throws him 
back to the people.
He leaves the people and his disciples only to come back to them
when they are in difficulties or when they are in need.
He takes LEAVE only to RE-ENTER