A quote that includes words about strength is "Men seem neither to understand their riches nor their strength. Of the former they believe greater things than they should; of the latter, less." by Francis Bacon. Another quote is "But what is strength without a double share of wisdom?"
Francis Bacon, who was born in 1561, lived as a statesman and philosopher in London. At one time, he held one of England's most dominant positions, Lord Chancellor.
The second quote is an extract from John Milton's drama "Samson Agonistes." Milton was born in 1608. Apart from serving as a civil servant in London, he also wrote various English poems that remain popular today.