Paraphrase Wordsworth's poem "My heart leaps up when I behold..."
MY heart leaps up when I behold
A rainbow in the sky:
So was it when my life began,
So is it now I am a man,
So be it when I shall grow old
Or let me die!
The child is father of the man:
And I could wish my days to be
Bound each to each by natural piety
The speaker says that their heart "leaps up" for joy, when he sees (beholds) a rainbow in the sky. Rainbows were in the sky when he was born, now that he is a man, and he hopes - if not, he'd rather die! - that they'll be there as he grows old.
The child is like the man's father, he says, because - if you look at it chronologically - the child grows into the father, and so is in a strange way "older", belonging to the past. And, as a child is "bound" (tied) to the man he becomes, Wordsworth's speaker hopes that each day of his life will be bound to the next with "natural piety" (piousness - respectfulness - for nature [or just, "that comes naturally"]).
Hope this helps!