This excerpt is from the poem, 'Sailing to Byzantium' by William Butler Yeats
Explanation:
The line "aged man is but a paltry thing, / a tattered coat upon a stick refers to an old man's soul.
The poet says the country he had left was a country of youth and so he has moved to the holy city of Byzantium. He calls the saints as masters and asks them to be his soul's singing masters.
He says his heart is a stick with desire and it is attached to a dying animal. Yeats speaks about the agony of old age.