Judah's request to Onan to marry his sister-in-law
after his brother, Er, died, states
And Judah said to Onan, Go in to your brotherís wife, and yabem her, and raise up seed to your brother.
Rashi clarifies the meaning of the underlined Hebrew word
yabem by citing an other verse where this
word is defined:
Dt25-05:06 discussing the childless widow states
If brothers live together, and one of them dies, and has no child,
the wife of the dead shall not marry outside to a stranger;
her husbandís brother shall yabem her, and take her to him for a wife, and perform the duty of a husbandís brother to her.
And it shall be, that the firstborn which she bears shall succeed
to the name of his brother who is dead,
that his name be not put out of Israel.
Using this other verse Rashi explains that the Hebrew
term yabem refers to a marriage of a childless widow by
a surviving brother-in-law in order to perpetuate the name of
the deceased. Rashi concludes that a similar usage exists
Advanced Rashi: Here the Bible uses a term,
yibum that predates the actual creation of this procedure.
Such foreshadowing is common in the Bible. For example
Gn02-01:04 mentions that God sanctified the Sabbath,
referring to the future Jewish custom of abstaining from
work on the Sabbath and making the day a holy day. Such foreshadowing
linguistically encourages respect for Biblical rituals.