The Book of Ruth, as you probably know, is one of the books in the Old Testament. According to the Wikipedia online encyclopedia:
The book tells of Ruth's accepting the God of the Israelites as her God and the Israelite people as her own. In Ruth 1:16 and 17 Ruth tells Naomi, her Israelite mother-in-law, "Where you go I will go, and where you stay I will stay. Your people will be my people and your God my God. Where you die I will die, and there I will be buried."
As far as allusions are concerned, the most famous allusion is contained in John Keats' masterpiece, "Ode to a Nightingale." In the next-to-last stanza of the poem the speaker says:
Thou wast not born for death, immortal Bird!
No hungry generations tread thee down;
The voice I hear this passing night was heard
In ancient days by emperor and clown:
Perhaps the self-same song that found a path
Through the sad heart of Ruth, when, sick for home,
She stood in tears amid the alien corn;
The same that ofttimes hath
Charm'd magic casements, opening on the foam
Of perilous seas, in faery lands forlorn.
The word "corn" does not means maize or Indian corn. The English use the word "corn" to apply to any kind of grain. Ruth is in such a strange new environment that even the grain in the fields is alien to her. Keats is stretching his imagination to the farthest extent The last two lines of that stanza are sometimes called "touchstone lines" because they represent the quintessence of poetry, and other poetry can be evaluated by comparing it with these inspired lines. In thinking of Ruth in this stanza, Keats is going as far back in time and space as he can imagine, and he is saying that the nightingale he hears that night is immortal and that it is the very same bird that was heard by Ruth in distant Israel some two thousand years ago.
Keats' "Ode to a Nightingale" ought to be acceptable as an excellent allusion to Ruth, because it is one of the most famous poems in the English language.