John Milton's poem, "On His Blindness," speaks to the frustrations Milton had regarding his lost sight. The poem reflects upon the idea that he (the speaker of the poem) will not be able to serve God now that his sight is gone. The following will show each line of the poem (or relevant groups of lines) and the meaning of the line/s following.
WHEN I consider how my light is spent,
The speaker is reflecting upon how his light (sight) has been used over his life. This could also refer to the speaker's spiritual light (given Milton's religious ideology).
Ere half my days in this dark world and wide,
The speaker has spent half of his life blind (meaning he knows what it means to see and feels loss at his sight being taken away).
And that one talent which is death to hide
Here, the talent the speaker refers to can be his ability to write (which may be lost now that his sight is gone), or it could refer to the God-given talents bestowed upon mankind by God.
Lodged with me useless, though my soul more bent
The speaker feels that his loss of sight has left him useless (to either write or serve God).
To serve therewith my Maker, and present
My true account, lest He returning chide,
'Doth God exact day-labour, light denied?'
There three lines refer to the speaker's desire to write and praise God, but, with his lost sight, he feels as if he cannot do either. (The speaker's writing could be referring to his desire to write for God.) The speaker is asking if God expects him to work given his light (sight) is gone.
I fondly ask.
Here, the speaker is asking for guidance in regards to how he should approach his concerns (his inability to write and write to praise God).
But patience, to prevent
That murmur, soon replies, 'God doth not need
Either man's work or his own gifts. Who best
Bear his mild yoke, they serve him best. His state
Is kingly: thousands at his bidding speed,
And post o'er land and ocean without rest;
They also serve who only stand and wait.'
In these last lines, the speaker receives the reply he has asked for. Patience replies to the speaker (given his patience with his blindness is lacking). Patience replies that it is not the work of man which pleases God. Instead, it is the "mild yoke" (those who are simply obedient to God) which makes God happiest.
For patience, God is happiest when mankind is able to spread God's word over "land and ocean without rest." The final line refers to the fact that it is far more important to praise God than to "stand and wait" (do nothing).