St. Thomas Aquinas
“It can be taken by way of metaphor, so that Christ’s Passion is understood by the chalice by way of comparison, because, like a cup, it inebriates, according to Lam. 3:15: ‘He hath filled me with bitterness, he hath inebriated me with wormwood’: hence our Lord Himself spoke of His Passion as a chalice, when He said (Mat. 26:39): ‘Let this chalice pass away from Me’: so that the meaning is: ‘This is the chalice of My Passion.’ This is denoted by the blood being consecrated apart from the body; because it was by the Passion that the blood was separated from the body.”
Source: St. Thomas Aquinas, Summa Theologica