Before the poem begins, the speaker includes a quotation from the Bible, specifically the Book of Genesis. This says that human beings were created in God's "own image"—that is, that all human beings are a reflection of God. Opening the poem with this quote makes the next lines all the more striking, since they describe a bent and broken man. This, the speaker seems to be asking, is what humanity has done to God's image?
The poem's opening lines then describe the titular "man with a hoe" referenced in the poem's title. This man's body has been deformed and his mind has been exhausted by years of intense physical labor. The use of "centuries" reveals that the speaker isn't talking about an actual person, however; rather, the man in the painting represents all working people from across humanity history. Essentially, this man symbolizes the oppression and exploitation of the working class in general.
The fact that his bent-over posture results from the strain of shouldering the "burden of the world" makes this oppression seem all the more unjust. The speaker is saying that laborers like this man produce the harvest that feeds humanity, yet this treatment is all the thanks they get.
The poem's first line also establishes its meter, which is iambic pentameter. This means that each line contains five iambs, or units made up of one long or stressed syllable and one short or unstressed syllable. However, this meter isn't perfect. The very first foot in the poem, "Bowed by," stresses the first instead of the second syllable, creating trochee. The stresses in the first line thus read as follows:
Bowed by | the weight | of cent- | uries | he leans
By beginning the poem in this way, the poet places extra emphasis on the meaning of the first word, a burst of sound that suggests the force of gravity bends the worker's body into a bow, like a piece of wood.
Alliteration and assonance also drive these lines forward, building the sense of how labor and time shape the worker's body. For example, the alliterative repetition of /h/ sounds (he; his hoe), /g/ sounds (gazes; ground), and /b/ sounds (back; burden) has the effect of identifying human features with tools and nature, suggesting how labor transforms the man's body into a tool in and of itself. Assonance in phrases such as "centuries he leans" and "ages in his face," highlight the changes in the worker's posture and facial expression as he labors over the course of long passages of time.