CIC 575 Many of Jesus’ deeds and words constituted a “sign of contradiction”,1 but more so for the religious authorities in Jerusalem, whom the Gospel according to John often calls simply “the Jews”,2 than for the ordinary People of God.3 To be sure, Christ’s relations with the Pharisees were not exclusively polemical. Some Pharisees warn him of the danger he was courting;4 Jesus praises some of them, like the scribe of Mark 12:34, and dines several times at their homes.5 Jesus endorses some of the teachings imparted by this religious elite of God’s people: the resurrection of the dead,6 certain forms of piety (almsgiving, fasting and prayer),7 the custom of addressing God as Father, and the centrality of the commandment to love God and neighbor.8

CIC 581 The Jewish people and their spiritual leaders viewed Jesus as a rabbi.9 He often argued within the framework of rabbinical interpretation of the Law.10 Yet Jesus could not help but offend the teachers of the Law, for he was not content to propose his interpretation alongside theirs but taught the people “as one who had authority, and not as their scribes”.11 In Jesus, the same Word of God that had resounded on Mount Sinai to give the written Law to Moses, made itself heard anew on the Mount of the Beatitudes.12 Jesus did not abolish the Law but fulfilled it by giving its ultimate interpretation in a divine way: “You have heard that it was said to the men of old. .. But I say to you. ..”13 With this same divine authority, he disavowed certain human traditions of the Pharisees that were “making void the word of God”.14

CIC 1824 Fruit of the Spirit and fullness of the Law, charity keeps the commandments of God and his Christ: “Abide in my love. If you keep my commandments, you will abide in my love.”15

CIC 2055 When someone asks him, “Which commandment in the Law is the greatest?”16 Jesus replies: “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind. This is the greatest and first commandment. And a second is like it: You shall love your neighbor as yourself. On these two commandments hang all the Law and the prophets.”17 The Decalogue must be interpreted in light of this twofold yet single commandment of love, the fullness of the Law:
The commandments: “You shall not commit adultery, You shall not kill, You shall not steal, You shall not covet,” and any other commandment, are summed up in this sentence: “You shall love your neighbor as yourself.” Love does no wrong to a neighbor; therefore love is the fulfilling of the law.18

CIC 2083 Jesus summed up man’s duties toward God in this saying: “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind.”19 This immediately echoes the solemn call: “Hear, O Israel: the LORD our God is one LORD.”20
God has loved us first. The love of the One God is recalled in the first of the “ten words.” The commandments then make explicit the response of love that man is called to give to his God.

CIC 2196 In response to the question about the first of the commandments, Jesus says: “The first is, ‘Hear, O Israel: The Lord our God, the Lord is one; and you shall love the Lord your God with all your heart, and with all your soul, and with all your mind, and with all your strength.’ The second is this, ‘You shall love your neighbor as yourself.’ There is no other commandment greater than these.”21
The apostle St. Paul reminds us of this: “He who loves his neighbor has fulfilled the law. The commandments, ‘You shall not commit adultery, You shall not kill, You shall not steal, You shall not covet,‘ and any other commandment, are summed up in this sentence, ‘You shall love your neighbor as yourself.’ Love does no wrong to a neighbor; therefore love is the fulfilling of the law.”22

1 Lk 2:34.
2 Cf. Jn 1:19; 2:18; 5:10; 7:13; 9:22; 18:12; 19:38; 20:19.
3 Jn 7:48-49.
4 Cf Lk 13:31.
5 Cf. Lk 7:36; 14:1.
6 Cf. Mt 22:23-34; Lk 20:39.
7 Cf. Mt 6:18.
8 Cf. Mk 12:28-34.
9 Cf Jn 11:28; 3:2; Mt 22:23-24, 34-36.
10 Cf. Mt 12:5; 9:12; Mk 2:23-27; Lk 6:6-g; Jn 7:22-23.
11 Mt 7:28-29.
12 Cf. Mt 5:1.
13 Mt 5:33-34.
14 Mk 7:13; cf. 3:8.
15 Jn 15:9-10; cf. Mt 22:40; Rom 13:8-10.
16 Mt 22:36.
17 Mt 22:37-40; cf. Deut 6:5; Lev 19:18.
18 Rom 13:9-10.
19 Mt 22:37; cf. Lk 10:27:“... and with all your strength.”
20 Deut 6:4.
21 Mk 12:29-31; cf. Deut 6:4-5; Lev 19:18; Mt 22:34-40; Lk 10:25-28.
22 Rom 13:8-10.