1.

The egg's no chick by falling from the hen;
Nor man a Christian, till he's born again.
The egg's at first contained in the shell;
Men, afore grace, in sins and darkness dwell.
The egg, when laid, by warmth is made a chicken,
And Christ, by grace, those dead in sin doth quicken.
The egg, when first a chick, the shell's its prison;
So's flesh to the soul, who yet with Christ is risen.
The shell doth crack, the chick doth chirp and peep,
The flesh decays, as men do pray and weep.
The shell doth break, the chick's at liberty,
The flesh falls off, the soul mounts up on high
But both do not enjoy the self-same plight;
The soul is safe, the chick now fears the kite.

2.

But chicks from rotten eggs do not proceed,
Nor is a hypocrite a saint indeed.
The rotten egg, though underneath the hen,
If crack'd, stinks, and is loathsome unto men.
Nor doth her warmth make what is rotten sound;
What's rotten, rotten will at last be found.
The hypocrite, sin has him in possession,
He is a rotten egg under profession.

3.

Some eggs bring cockatrices; and some men
Seem hatch'd and brooded in the viper's den.
Some eggs bring wild-fowls; and some men there be
As wild as are the wildest fowls that flee.
Some eggs bring spiders, and some men appear
More venom'd than the worst of spiders are.[16]
Some eggs bring piss-ants, and some seem to me
As much for trifles as the piss-ants be.
Thus divers eggs do produce divers shapes,
As like some men as monkeys are like apes.
But this is but an egg, were it a chick,
Here had been legs, and wings, and bones to pick.

John Bunyan

http://www.poemhunter.com/poem/meditations-upon-an-egg/