The School of Christian Perfection is an excellent compilation of the teachings of Saint Alphonsus on how to become a saint. We recommend this volume along with Saint Alphonsus' commentary on I Corinthians 13 entitled Charity. Let us consider this extract: "St. Catherine of Genoa once said to Our Lord: “O my God, Thou commandest me to love my neighbor, and I can love no one but Thee.” Our Saviour replied: “My daughter, whoever loves Me loves everything that is loved by Me.” Why, therefore, must we love our neighbor? Because he is loved by God. St. John was therefore right when he called him a liar who says that he loves God but hates his neighbor. Our Lord has promised that He will regard as done to Himself what we do for the least of our brethren: “Amen I say to you, as long as you did it to one of these, my least brethren, you did it to me.” (Matt. 25:40). From this St. Catherine of Genoa concludes: “If you wish to know how much a person loves his God, see how much he loves his neighbor.”"