Shavua Tov. The number 13 is not considered an unlucky number in Judaism. It is used in several significant situations.

Everyone is aware that 13 is the age of Bar Mitzva. This is when a young man is considered mature enough to take upon himself the observance of Mitzvot.

Thirteen represents the Thirteen Principles of Faith of the Rambam, where he lays down the basic tenements of Judaism.

There are also the Thirteen Atteibutes of Hashem or י״ג מידות, that allows us to receive G-d’s mercy rather than strict judgement.

There are also the Thirteen methods of deriving the Torah, brought by Rabbi Yishmael, that we recite each morning in our prayers.

Today’s Parsha alludes to the Thirteen Sacrifices offered in the Temple. Five were meal offerings, or מנחה, and eight were offered from animals. Three of the eight were eaten by the one offering, the Pesach sacrifice, the מעשר בהמה, when a tenth of newborn cattle were offered each year, and the תודה, thanksgiving offering. The עולה, חטאת, and אשם, were eaten by כהנים or burned on the altar. The two remaining sacrificed were the בכור and שלמים.

So we see the number 13 is a very significant number in Judaism!