This week's Torah portion, Ki Tisa, contains two pivotal events in the relationship between the Almighty and the Jewish people:
the sin of the Golden Calf and subsequently gaining forgiveness for that sin (articles 3 - 5).
The 2nd article relates to the famous Shabbat section (31:12-17) in the Reading.
We also read an additional Torah section in Shul, called "Parah" (article 5) in preparation for the Passover Festival.