Deuteronomy 6 (the first paragraph of Shema)
4 Hear, O Israel- The LORD our God, the LORD is one. 5 Love the LORD your God with all your heart and with all your soul and with all your strength. 6 These commandments that I give you today are to be upon your hearts. 7 Impress them on your children. Talk about them when you sit at home and when you walk along the road, when you lie down and when you get up. 8 Tie them as symbols on your hands and bind them on your foreheads. 9 Write them on the doorframes of your houses and on your gates.
Leviticus 19
18 ” ‘Do not seek revenge or bear a grudge against one of your people, but love your neighbor as yourself. I am the LORD.
Shabbat 31a
On another occasion it happened that a certain heathen came before Shammai and said to him, ‘Make me a proselyte, on condition that you teach me the whole Torah while I stand on one foot.’ Thereupon he repulsed him with the builder’s cubit which was in his hand. When he went before Hillel, he said to him, ‘What is hateful to you, do not to your neighbour- that is the whole Torah, while the rest is the commentary thereof; go and learn it.’
Mark 12
28One of the teachers of the law came and heard them debating. Noticing that Jesus had given them a good answer, he asked him, “Of all the commandments, which is the most important?”
29″The most important one,” answered Jesus, “is this- ‘Hear, O Israel, the Lord our God, the Lord is one. 30Love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.’ 31The second is this- ‘Love your neighbor as yourself.’ There is no commandment greater than these.”