Virtue against fury
Shall take up arms; and the fight be short;
For ancient valour
Is not dead in Italian hearts. (26.8)
Machiavelli's little book ends with these four lines from Petrarch's famous Canzone 128 "Italia mia." Petrarch was a famous Italian poet—maybe the most famous Italian poet aside from Dante—who lived in the 1300s and was one of the first humanists. Ending with Petrarch situates Machiavelli firmly in that humanist tradition.
There's more. Machiavelli has just spent several paragraphs begging Lorenzo de' Medici to take on the huge task of unifying Italy under the rule of his family. At this point Italy had been inundated by invasions from France, Spain, and Germany for decades, and it looked like there was no end in sight. Not only that, but all the small Italian city-states were constantly at each other's throats, trying to beat the others. Machiavelli called on Lorenzo to kick these intruders out, stop the infighting, and create peace on the peninsula.
Petrarch's poem was written in similar times. In the winter of 1344-45, the poem describes Italians fighting amongst each other with German mercenaries, tearing the peninsula apart with war. Besides being one of the most famous Italian anti-war poems, Canzone 128 is one of the first examples ever of peninsular Italian pride (that's pride for the whole boot) instead of local Italian pride, which would've gone along with Machiavelli's theme of unifying Italy. The poem ends with Petrarch calling out the word pace, or peace, three times.
If ever there was a perfect poem for what Machiavelli is trying to say, this is it.
Since even little kids in kindergarten learned at least part of Canzone 128, Machiavelli's appeal to Lorenzo is super emotional and patriotic. We imagine the emotion he was trying to create is the same one that those people who cry during the national anthem feel. Unfortunately for Machiavelli (and for Petrarch), his strategy doesn't seem to have worked too well. Peace and unity wouldn't come to Italy for hundreds of years.