Following in the steps of the prophets and John the Baptist, Jesus announced the judgement of the Last Day in his preaching. Then will the conduct of each one and the secrets of hearts be brought to light. Then will the culpable unbelief that counted the offer of God's grace as nothing be condemned. Our attitude to our neighbour will disclose acceptance or refusal of grace and divine love. On the Last Day Jesus will say: "Truly I say to you, as you did it to one of the least of these my brethren, you did it to me."
Source: Catechism of the Catholic Church (Vatican.va)