What does prison mean spiritually?

Though God be good and free be heaven,

No force divine can love compel—

And though the song of sins forgiven

May sound through lowest hell—

The sweet persuasion of His voice

Respects thy sanctity of will.

He giveth day—thou hast thy choice

To walk in darkness still—

As one who turning from the light,

Watches his own gray shadow fall,

Doubting upon his path of night,

If there be day at all!

No word of doom may shut thee out,

No wind of wrath may downward whirl,

No swords of fire keep watch about

The open gates of pearl—

A tenderer light than moon or sun,

Than song of earth a sweeter hymn,

May shine and sound forever on,

And thou be deaf and dim.

Forever round the Mercy-seat

The guiding lights of love shall burn—

But what if habit-bound thy feet

Shall lack the will to turn?

What if thine eyes refuse to see,

Thine ear of heaven's free welcome fail,

And thou a willing captive be,

Thyself thy own dark jail?

O doom beyond the saddest guess,

As the long years of God unroll

To make thy dreary selfishness

The prison of a soul!

To doubt the love that fain would break

The fetters from thy self-bound limb,

And dream that God can thee forsake

As thou forsakest Him!

—John Greenleaf Whittier