On that day, many will come to me shouting “Lord…Lord” and telling me that they did miracles and prophesied in my name, but I will tell them to depart from me because I never knew them. How do we prove that we know the Lord? Is it by calling his name with loud voices? It is certainly not by prophesying and performing miracles, at least if we go by what Jesus says in today’s Gospel passage. But such a conclusion would be wrong, for it is the Lord himself who promised his followers the ability to perform miracles and mighty deeds in his name (cf. Mark 16:17-18; John 14:12). The point that the Lord was making is that there is much to knowing him than performing mighty acts. We can say with certainty that we know the Lord only if the Lord knows us. But how will the Lord get to know us?
In the Matthean final judgment scene (cf. Matthew 25:31-46), we are given a peek into what constitutes being known by the Lord: “In truth I tell you, as long as  your eyes were open to the least of my brothers,  there I was, in their midst.” The Lord is known  through his family, in his brothers and sisters, for without them, the Lord ceases to be. He/she who claims to know the Lord must know the Lord’s brothers and sisters. In other words, the Lord is known through those for whom he laid down his life. Knowledge of the Lord consists, not in the gift of tongues for its own sake, but rather in the gift of tongues that changes for the better the life of another. So yes, the knowledge of the Lord consists in the performing of mighty deeds, but only if such acts lift the fallen from where they are lying or when the mighty acts performed lead to the feeding of the hungry.