How Parshas Balak almost became part of the daily Shema:

The Talmud[1] relates that the sages had originally desired to establish the portion of Balak as the third paragraph of the Shema due to it containing the words Kara Shachav Keari Ukilavi Mi Yekimenu, which refers to the Jewish people going to sleep and awakening which is similar to the Shema obligation which is to be recited in the morning and evening.[2] Why then did they not establish this paragraph? Because it is too long and that would be too difficult on the congregation. The Talmud explains that it is not possible to recite just that verse as it is forbidden for one to stop in the middle of a paragraph.

The following is the text from the Talmud:

Rabbi Abbahu son of Zutarti said in the name of Rabbi Yehuda bar Zevida: They sought to establish the portion of Balak (which includes Balaam’s prophecies) as part of the daily Shema reading. Why was it not established? Because of the burden on the congregation. What is the reason? If you say it’s because it mentions the Exodus from Egypt—Then let them read the portion of interest or the portion of weights, which also mention the Exodus. Rather, Rabbi Yosei bar Avin said: It’s because of the verse:
“He crouched, he lay down like a lion, and like a lioness—who shall rouse him?” So why not just read that verse alone? Because we have a tradition: Any portion that Moses divided, we may divide.
Any portion that Moses did not divide, we do not divide. Regarding the portion of Tzitzit (fringes)—why was it established in the Shema? Rabbi Yehuda bar Chaviva said: Because it contains five key themes:

1. The commandment of Tzitzit
2. The Exodus from Egypt
3. The yoke of commandments
4. A warning against heretical beliefs
5. A warning against sexual transgression and idolatry

[1] Brachos 12b

[2] Rashi ibid.