For what purpose does Milton use the element of allusion in "When I consider how my light is spent"

Milton, like many other poets of his era, often alludes
either implicitly or explicitly (as in this poem) to the Bible.  The Bible was the
best-known text of this period. Some people (such as Milton himself) studied it deeply
for most of their lives, and even relatively uneducated people would have known the
Bible by hearing about it in sermons and even in everyday
conversation.

Therefore, by alluding to the Bible, Milton
achieves several important results:

1. He employs a
   source of authority that practically everyone in his culture would have accepted as the
   most important authority. He thus gives added authority to his
   poem.


2. He shows his desire, as a Christian but especially
   as a Protestant, to ground his writings in the scriptural word of
   God.


3. He shows the continuing relevance of God’s words to
   the particular lives of particular persons.


4. He adds to
   the complexity of his poem by creating a kind of dialogue within the work between his
   poem and the master-text of his culture.