St. Thomas Aquinas
“Because last words, chiefly such as are spoken by departing friends, are committed most deeply to memory; since then especially affection for friends is more enkindled, and the things which affect us most are impressed the deepest in the soul. Consequently, since, as Pope Alexander I says, ‘among sacrifices there can be none greater than the body and blood of Christ, nor any more powerful oblation’; our Lord instituted this sacrament at His last parting with His disciples, in order that it might be held in the greater veneration.”
Source: St. Thomas Aquinas, Summa Theologica