"O mio babbino caro" ("Oh my dear papa") is a soprano aria from the opera Gianni Schicchi (1918) by Giacomo Puccini to a libretto by Giovacchino Forzano. It is sung by Lauretta after tensions between her father Schicchi and the family of Rinuccio, the boy she loves, have reached a breaking point that threatens to separate her from Rinuccio.
Here is an arrangement for String Quartet.
The PDF file contains the score and all parts.