What possibly could have inspired the Mishnah to consider using Balaam as a foil to accentuate the ideal qualities of Avraham?
All who have these three qualities is of the students of Avraham our father; and three other qualities is of the students of Balaam the wicked. A good eye (generous spirit), humble spirit, and a lowly soul (likely, modesty is intended) – [those who possess these qualities are of the students of Avraham]; An evil eye (miserliness), a haughty spirit, and avarice – these are the students of Balaam the wicked… (Mishnah Avot 5:22)
Clues to this mystery can be found thanks to the discerning eyes of the rabbinic sages. Through close reading and comparison of the language used by the Torah in its telling of the story of the Akedah (the binding of Yitzhak), together with the language used in the story of Balaam’s mission to curse the children of Israel, the sages seemed to have noticed that the Torah apparently played one story off of the other.
One example will suffice. Notice how the Torah describes the initial journeys of these two biblical characters in fulfillment of their missions. Avraham’s journey to the Akedah starts off:
And Avraham rose (vayashkeim) early in the morning and saddled his donkey (hamoro) and took his two lads with him and Isaac his son, and he split wood for the offering, and rose and when to the place that God had said to him. (Genesis 22:3)
Balaam’s mission to curse Israel begins:
And Balaam rose (vayakom) early in the morning and saddled his ass (atono), and he went with the chieftains of Moab (Numbers 22:21)
The beginnings of each of these two sentences are virtually the same, inspiring the sages to compare Avraham and Balaam. (The opening verbs are “vayashkeim” and “vayakom” are “synonymous; The two also saddle donkeys: Avraham, a male donkey; Balaam a female donkey. The later difference is the impetus for some colorful rabbinic jokes at Balaam’s expense.)
The similarity between these two verses inspired the following midrash, found in a Talmudic period midrashic collection, in the name of a prominent sage from the period of the Mishnah:
Said Rabbi Shimon bar Yohai: Love makes a person act strangely; similarly, hatred makes people act strangely. Love makes people act strangely – ‘And Avraham rose (vayashkem) early in the morning and saddled his donkey (hamoro)’; Hatred makes people act strangely – ‘And Balaam rose (vayakom) early in the morning and saddled his ass (atono)’. But didn’t each of them have many servants [who could have saddled their animals for them]? Rather hatred makes people do strange things and love makes people do strange things… (adapted from Genesis Rabbah 55:5, Theodore-Albeck ed. pp. 592-3)
Rabbi Shimon bar Yohai used the similarity between these two verses to point out that certain extreme emotions, in this case, love and hatred, cause people to veer from their normal behavior. For our purposes, though, this midrash also bears witness that during the period of the Mishnah, the linguistic parallels found in these two stories, inspired a comparison of the virtues and vices attributed to Avraham and Balaam, all in order to inspire people to choose the life of virtue over that of vice, or, in other words, to choose to be a disciple of Avraham, and not of Balaam.