Shabbat Parshat Bamidbar

According to the calendar system we have in place, Parshat Bamidbar is always read before Shavuot. It’s usually read on the Shabbat beforehand but sometimes, Naso is read on the Shabbat beforehand.

See Tractate Shabbat 86b and on, that according to the sages, the Torah was given on the sixth of Sivan, whereas in the opinion of Rabbi Yossi, it was given on the seventh on Sivan.

See Likutei Sichot vol. 18, page 18 for the connection between the parsha and Shavuot.