The haftorah for the Torah reading on [the first day of] Shavuot, chosen by the Sages thousands of years ago, is the primary biblical source material in the study of Kabbalah;
The lead article offers some definitions, while articles 2-4 are based on the Zohar, the Arizal and the Ramak respectively.
The 3rd article is for the first chapter of Pirkei Avot, for those who continue to study it on Shabbat afternoons throughout the summer,
while articles 5-7 relate to the weekly Torah reading, Naso.

(Those of you in ISRAEL should click to Beha'alotecha for articles on the Weekly Reading there.)