The two readings in today's Mass complements each other well. Whereas it is said in Romans 3:28 that "a person is justified in faith" - faith in Jesus Christ, Jesus supplements it by suggesting that faith alone is not enough and we have to put our faith into action.
The reading today (Matthew 7:21-27) begins with Jesus saying: "Not everyone who says to me, 'Lord, Lord,’ will enter the kingdom of heaven, but only the one who does the will of my Father in heaven." He then makes use of the parable of the house on rock and the house on sand to illustrate the difference between the one who listens to His words and acts on them and the one who listens but does not act on them. When the rain falls, the flood comes and the winds blows, he house of the former does not collapse because it has been set solidly on rock but the other one does and is completely ruined.
Jesus warns that, come judgement day, those of us who do not do the will of God will be turned away by Him.
So our faith should be supported by our action.