The lines you are quotes are taken from the first poem in Il Canzoniere by the Italian poet Francesco Petrarch. This book, titled Rime Sparse (Scattered Rhymes) or Il Canzoniere (Song Book), was written in Italian and consist of a group of relatively short love poems addressed to his beloved Laura. Most of the poems in the book, including the one you quoted, are sonnets. In fact, this is the book from which the Petrarchan (i.e. `pertaining to Petrarch’) sonnet got its name. What you are quoting, however, is not the Italian original but an English translation. In this particular case, the translator did not follow the original rhyme scheme. Instead, this is a fairly literal translation that does not preserve the meter or rhyme of the original.