As we near the end of the poem, the past and the present start to fade away from Whitman. He's concerned about what's next.
He's only going to stay another minute, so he'd better speak honestly before he snuffs out his evening candle and goes to bed.
Here is one of the poem's most famous and representative lines: "Do I contradict myself? Very well then . . . . I contradict myself; I am large . . . . I contain multitudes."
In analytic philosophy (the traditional philosophy practiced in England and the US), contradicting yourself is a thing to avoid at all costs. Whitman embraces contradiction. He is large enough to contain contradictory things.
The day is ending, and he wants to know who will be done with dinner to take a walk with him.
We're running out of time to talk with him. He has been doing all the talking, and we'd better speak up fast before he leaves.