On the day of Shavuot (Pentecost) the scroll of Ruth is read in every synagogue. There are various reasons proposed for this. I think one reason may be related to the Law, which tradition says was given on this date.
Ruth was from Moab. She was married to an Israelite for about ten years, until he died. Naomi, her mother-in-law determined to go home. Because Jewish law said that the nearest living male relative would have to raise an heir to the daughters-in-law, and apparently Moabitish law did not, she gave them both the opportunity to stay in their homeland. This became the occasion for the beautiful passage where Ruth says to Naomi:
Entreat me not to leave thee, or to return from following after thee: for whither thou goest, I will go; and where thou lodgest, I will lodge: thy people shall be my people, and thy God my God: Where thou diest, will I die, and there will I be buried: the LORD do so to me, and more also, if ought but death part thee and me. (Ruth 1:16-17)
Herein is a reason the scroll of Ruth is appropriate to be read on Shavuot. Ruth declares her intention to follow the nation of Israel, and their God. She does this willingly, and even in the face of her mother-in-law's repeated insistence that she remain in her native land. Ruth, then, typifies the entire nation to which she aspires.
Israel was enslaved in Egypt. The people of Moses' time had been born there. They knew no other land. Along comes Moses, and they began a journey of the body and the spirit that would take them away from all they had ever known.
Fifty days later they were at the foot of Sinai. They were in a desert, with only two ways to go-back to Egypt or forward into the unknown. God gives them the choice of which way to go. "Now therefore, if ye will obey my voice indeed, and keep my covenant, then ye shall be a peculiar treasure unto me above all people: for all the earth is mine: And ye shall be unto me a kingdom of priests, and an holy nation." (Ex 19:5-6) Without even knowing the conditions of that covenant, "all the people answered together, and said, All that the LORD hath spoken we will do." (Ex 19:8) The people said to Moses, in essence, "thy God shall be my God."
Ruth had the advantage that she knew what she was getting into. But she typifies Israel in that she chose to leave the land of her birth to follow a God she had not previously known.
That she took her vow seriously can be seen in Ruth 3:10. Although she was obviously an attractive "older lady," she did not marry outside the family, but kept herself for the near kinsman who would raise up an heir for her dead husband. Not only had she promised to follow her mother-in-law, but she learned the Law and kept it.
As Israel chose to keep the Law given at Sinai on Shavuot, and merited to be called God's chosen people through whom the Messiah would come, so Ruth also chose to keep God's law, even in the small details. As a result, she merited to be the mother of David's line, and thus of the direct lineage of Messiah.
(Shavuot/Pentecost falls on May 28, 2001.)