BS"DBack to chapter 35 about pride
Translated by Ralph Anzarouth and an anonymous friend
Abstinence involves purifying oneself and refraining from anything unclean or repulsive and restraining the desire aroused by these things.
This trait can be compared to the wild donkey, which will not drink water unless it appears clear and pure. Moreover, if it goes to the river and finds the water cloudy, it will wait for two or three days without drink until the water becomes clear.
King Solomon said (Proverbs 20, 3): "It is honor for a man to refrain from quarreling, and every fool will be exposed1." He further said (ibid. 20, 17): "Bread of falsehood is sweet to a man, but afterwards his mouth will be filled with gravel1." Our sages of blessed memory said (Talmud Bavli, tractate Avoda Zara 20b): "Rabbi Pinchas ben Yair said: Torah brings one to caution, etc. cleanliness brings to abstinence, abstinence brings to purity etc.". They also said in tractate Baba Batra that when the [holy] Temple was destroyed, more and more Pharisees decided to abstain from marriage, from eating meat and from eating wine, etc.
The wise [King David] said (Psalms 32, 9): "Like a horse, like a mule […] whose mouth must be held with bit and bridle1," in the same way, man also needs abstinence. Varo said: "Abstinence is the way to achieve all the virtues".
The ancients related that Alexander of Macedon was once crossing the Babylonian desert and ran out of provisions because of the length of the journey: there was no bread in all that region and many of his man had already died of hunger. One of the horsemen from his company found a honeycomb and brought it to the king. Alexander took it and threw it into the river and said: "Heaven forbid that I should live while all those accompanying me would die". A lot of his men threw themselves into the river in order to take the some of the honey and most of them drowned and died because of their weakened condition. They did not travel much further until they came to an inhabited place where they found all they needed and he and his men ate and drank and were revived. Thus, those who were patient and restrained themselves survived, while those who rushed to fulfill their craving died in humiliating circumstances.
Note of the translators:
 Translation of this verse courtesy of Judaica Press and chabad.org
The whole book Tzemach Tzadik in Hebrew (printed in Rashi characters) can be downloaded in PDF format and read online at Hebrewbooks.org. Chapter 36 about Abstinence is found at pages 70-71.