On what page of banner in the sky does it say it is the ultimate wisdom of the mountain that a man is never more a man than when he...?

It is not from Banner in the Sky at all but from a LIFE article Ullman wrote in 1945.

"That men have climbed the Matterhorn and McKinley, Aconcagua and Nanda Devi — and that they will eventually climb Everest itself — means little. That they should want to climb them and try to climb them means everything. For it is the ultimate wisdom of the mountains that a man is never more a man than when he is striving for what is beyond his grasp, and that there is no conquest worth winning save that over his own weakness and ignorance and fear."