Three Pilgrimage Festivals

The Three Pilgrimage Festivals or Shalosh Regalim (שלוש רגלים, or חַגִּים), are three major festivals in Judaism—two in spring; Passover, 49 days later Shavuot (literally 'weeks', or Pentecost, from the Greek); and in autumn Sukkot ('tabernacles', 'tents' or 'booths')—when all Israelites who were able were expected to make a pilgrimage to the Temple in Jerusalem as commanded by the Torah. In Jerusalem, they would participate in festivities and ritual worship in conjunction with the services of the kohanim (priests) at the Temple.

All three coincide with important harvest times in the Land of Israel: Passover with the barley harvest, Shavuot with the harvesting of the wheat, and the eighth day of Sukkot marks the conclusion of the fruit harvest.

After the destruction of the Second Temple, the actual pilgrimages are no longer obligatory upon Jews, and no longer take place on a national scale. During synagogue services, the related passages describing the holiday being observed are read aloud from a Torah scroll on the bimah (platform) used at the center of the synagogue services. During the Jewish holidays in the state of Israel, many observant Jews living in or near Jerusalem make an effort to attend prayer services at the Western Wall, emulating the ancient pilgrimages in some small fashion.

Samaritans make pilgrimages to Mount Gerizim three times a year to this day.

Sources in the Hebrew Bible
"Three times a year you shall hold a festival for Me: You shall observe the Feast of Unleavened Bread—eating unleavened bread for seven days as I have commanded you—at the set time in the month of Abib, for in it you went forth from Egypt; and none shall appear before Me empty-handed; and the Feast of the Harvest, of the first fruits of your work, of what you sow in the field; and the Feast of Ingathering at the end of the year, when you gather in the results of your work from the field. Three times a year all your males shall appear before the Sovereign, יהוה."
 * Book of Exodus

"You shall observe the Feast of Unleavened Bread—eating unleavened bread for seven days, as I have commanded you—at the set time of the month of Abib, for in the month of Abib you went forth from Egypt. Every first issue of the womb is Mine, from all your livestock that drop a male as firstling, whether cattle or sheep. But the firstling of an ass you shall redeem with a sheep; if you do not redeem it, you must break its neck. And you must redeem every male first-born among your children. None shall appear before Me empty-handed. Six days you shall work, but on the seventh day you shall cease from labor; you shall cease from labor even at plowing time and harvest time. You shall observe the Feast of Weeks, of the first fruits of the wheat harvest; and the Feast of Ingathering at the turn of the year. Three times a year all your males shall appear before the Sovereign יהוה, the God of Israel." "1 Observe the month of Abib and offer a passover sacrifice to your God יהוה, for it was in the month of Abib, at night, that your God יהוה freed you from Egypt. 9 You shall count off seven weeks; start to count the seven weeks when the sickle is first put to the standing grain. 10 Then you shall observe the Feast of Weeks for your God יהוה, offering your freewill contribution according as your God יהוה has blessed you. 13 After the ingathering from your threshing floor and your vat, you shall hold the Feast of Booths for seven days. 16 Three times a year—on the Feast of Unleavened Bread, on the Feast of Weeks, and on the Feast of Booths—all your males shall appear before your God יהוה in the place that [God] will choose. They shall not appear before יהוה empty-handed, 17 but each with his own gift, according to the blessing that your God יהוה has bestowed upon you."
 * Book of Deuteronomy:

Other biblical references
In his vision of a restored Jerusalem, the prophet Isaiah refers to Zion as "the city of our appointed feasts,". Zechariah foretells a messianic era when all nations will come to Jerusalem for the feast of Sukkot. The Song of Ascents or pilgrim psalms (Psalms 120-134) are associated with the pilgrims' journey to Jerusalem.