The text of his Angelus follows, via Zenit, with my emphases:
The biblical readings for the Mass this Sunday center on the theme of fraternal charity in the community of believers, which has its source in the communion of the Trinity. The apostle Paul affirms that the whole Law of God has its fullness in love in such a way that in our relationships with others, the 10 Commandments and every precept are summed up thus: "You will love your neighbor as yourself" (cf. Romans 13:8-10). The Gospel text, taken from Matthew 18, which treats of the life of the Christian community, tells us that brotherly love also includes reciprocal responsibility, on account of which, if my brother sins against me, I must be charitable to him and, first of all, speak with him personally, showing him that that what he said or did is not good. This way of behaving is called fraternal correction: it is not a reaction to the offense I have suffered but a being moved by love for my brother. St. Augustine comments: "He who has offended you, in offending you, he has caused himself a grave injury, and will you not care for the wound of your brother? […] You must forget that you have been offended but not your brother’s wound" (Sermon 82, 7).
And what if my brother does not listen to me? In today's Gospel, Jesus indicates a gradual approach: first go back and talk to him with two or three other persons so as to help him better grasp what he has done; if despite this he rejects the observation, the community must be told; and if he does not listen to the community either, it is necessary to make him see the rupture that he himself has provoked, separating himself from the Church. All of this shows that there is a co-responsibility in the journey of the Christian life: everyone, conscious of his own limits and defects, is called to welcome fraternal correction and to help others with this particular service.
Another fruit of charity in the community is unified prayer. Jesus says: "If two of you on earth agree to ask for something, my Father who is in heaven will grant it. Because wherever two or three are gathered in my name, there I am in their midst" (Matthew 18:19-20). Personal prayer is certainly important, indeed indispensable, but the Lord assures his presence in the community that -- even if it is very small -- is united and of one accord, because it reflects the reality itself of God One-and-Three, perfect communion of love. Origen says that "we must play in this symphony" (Commentary on the Gospel of Matthew 14:11), that is, within this concord of the Christian community. We must participate both in fraternal correction, which requires much humility and simplicity of heart, and in prayer, that it might rise up to God from a community truly united in Christ.
Let us plead for all of this through the intercession of Mary Most Holy, Mother of the Church, and of St. Gregory the Great, Pope and Doctor, whom we commemorated in yesterday’s liturgy.