'The shoulder' signifies all power. In Ezekiel 29:7, this signifies the power or faculty of understanding truth. 'To dwell between his shoulders,' as in Deuteronomy 33:12, signifies being in security and power.

(Odkazy: Arcana Coelestia 1085)

5812. 'The boy cannot leave his father' means that that truth cannot be separated from spiritual good. This is clear from the meaning of 'leaving' as being separated; from the representation of 'Israel' as spiritual good from the natural, dealt with in 4286, 4598, 5807; and from the representation of 'Benjamin' as new truth, dealt with in 5804, 5806. This truth is called 'the boy' because it is born last; for this truth is not born until a person has become regenerate. At this point he receives newness of life through this new truth joined to good, which also is why this truth is meant by 'a child of his old age, the youngest one', 5804.