'A hand-breadth' signifies conjunction of truth from the divine.

(Ссылки: Arcana Coelestia 9534)

55. But He laid His right hand on me. This symbolizes life then infused from the Lord.

The Lord laid His right hand on him because a communication is effected through the touch of the hands. That is because the life of the mind and so of the body projects itself into the arms and through them into the hands. It is on this account that the Lord touched with His hand the people He brought back to life and healed (Mark 1:31, 41; 7:32-33; 8:22-26; 10:13, 16).

The fundamental reason for this is that the Lord's presence in a person is an adjunction, thus a conjunction by contiguity, and this contiguity becomes closer and fuller in the measure that the person loves the Lord, which is to say, as he keeps His commandments.

From these few observations it can be seen that the Lord's laying His right hand on John means, symbolically, that He infused His life into him.