'Stone Walls Do Not A Prison Make' by Richard Lovelace.

In very brief summary, these lines from the poem by Richard Lovelace mean that it takes more than physical limits to imprison a person's mind or soul. Stone walls and iron bars may prevent a person from moving freely in their body, but if they can still love freely whoever they want, and have free emotions and let their thoughts fly free, then in heart, mind and soul - they are free. the poet seems to believe that these latter freedoms are more important. The poem is about freedom and has similarities with Gerard Manley Hopkins poem about The Skylark.

1618-1657 Richard Lovelace was born in London, at Woolwich and came from a military background. His family were from kent which is in the very south of England.

If you would like to do some extension reading to broaden your knowledge of the subject of freedom/spirituality in poetry, Hopkins is an interesting comparison:

Lovelace actually wrote this poem while imprisoned, which I believe might help you decipher the meaning of these lines and the poem as a whole.  Let's look at the first two lines first--stone walls do not a prison make/nor iron bars a cage: what is the image your mind produces after reading these?  I picture a prisoner being literally walled or caged in.  Now...let's go to the third line: minds innocent and quiet take.  He's taking us out of that physical imprisonment and putting us into our own minds.  And then, finally, "that for ahermitage".  Dictionary.com defines hermitage as "any secluded place of residence or habitation".  So, what Lovelace is saying is that he may be physically imprisoned, but no one can lock up his thoughts or imagination.  Because of this, he is still free--to think, dream, and give his opinions.

What Richard Lovelace is saying here is that your mind is what determines how you look at any particular situation.  The lines you quote are from his poem "To Althea, from Prison" written in 1642.

If you look at the lines you cite, he is saying that it's not the physical surroundings that make a place a prison.  He says that if you have the right frame of mind -- if your mind is innocent and quiet, then what others see as a prison is actually a refuge (a hermitage).

He may be speaking literally about prison here (he was actually in prison when he wrote this) but the broader meaning is that your state of mind determines whether you are going to see your current circumstances as good or bad.