Rachel Estée Sam and William Josiah Rubenstein are to be married Sunday at the Boston Harbor Hotel in Boston. Rabbi Moshe Waldoks will officiate, incorporating blessings in Hebrew, English, French and Cambodian. On Saturday a traditional Khmer wedding celebration was held at the Sunny Da restaurant in Lowell, Mass., that included a pairing ceremony, during which ribbons representing blessings were tied on the wrists of the bride and groom.