“Watch for phonies, keep your enemies close nigga watch your homies”

Machiavelli commented on the relative ease of gaining favor from friends and enemies in Chapter 20 of The Prince, quoted above. However, this particular wording comes from a line spoken by Michael Corleone in The Godfather Part II (1974), written by Mario Puzo and Francis Ford Coppola:
My father taught me many things here. He taught me in this room. He taught me: keep your friends close, but your enemies closer.
Misattributed

This has often been attributed to Sun Tzu and sometimes to Petrarch. It comes most directly from a line spoken by Michael Corleone in The Godfather Part II (1974), written by Mario Puzo and Francis Ford Coppola:
My father taught me many things here. He taught me in this room. He taught me: keep your friends close but your enemies closer.
Niccolò Machiavelli, who is also sometimes credited, wrote on the subject in The Prince:
It is easier for the prince to make friends of those men who were contented under the former government, and are therefore his enemies, than of those who, being discontented with it, were favourable to him and encouraged him to seize it.
Misattributed

Source: The Goblin Quest Series, Goblin Hero (2007), Chapter 7 (p. 117)

Canto XXX, line 103 (tr. Longfellow).
The Divine Comedy (c. 1308–1321), Purgatorio

Source: yt

First lines, Ch. 1
The Crimson Petal and the White (2002)
Context: Watch your step. Keep your wits about you; you will need them. This city I am bringing you to is vast and intricate, and you have not been here before. You may imagine, from other stories you've read, that you know it well, but those stories flattered you, welcoming you as a friend, treating you as if you belonged. The truth is that you are an alien from another time and place altogether.

Source: City of Fallen Angels