In this way the love of God is revealed to us: God sent his only Son into the world so that we might have life through him. The Solemnity of the Most Sacred Heart of Jesus which the universal Church observes today is a celebration of God's love. It is a celebration of God's love that is radiated to the world through God's Son Jesus Christ. In Jesus Christ, God's love has been expressed in its fullness (cf. John 3:16). It is a love that encompasses the entirety of Jesus' saving mission, from his birth through his passion and death and to his glorious rising from the dead. In other words, the fullness of God’s love for the created world is demonstrated in Jesus faithfully living out his incarnation: when he fed the hungry, healed the sick and forgave sinners, and when he gave his life for his brothers and sisters as he hung upon the wood of the cross (cf. Second Reading). This is the love which we call to mind every time we gather in praise and worship to celebrate the Eucharist. However, we celebrate this feast, not only to marvel at God's love for us in Jesus Christ, but also to remind ourselves of what we are called to be: a people of love.
In the First Reading, Moses is reminding the Israelites that love is the reason for their election as God's favorite. It is a love that has consistently been demonstrated in action and out of fidelity to God's promises. God had promised to love Israel, to be there for her and to act on her behalf. It is thus that God ransomed them from slavery in Egypt and settled them in their own land. But Moses also reminds the sons and daughters of Israel that the reason for God's acts of love towards them is that they too are made free to love. God loved them so that, in turn, they too could love. This is the point that St. John picks up in the Second Reading:  Beloved, if God so loved us, we also must love one another. 
Loving becomes our demonstration that we are recipients of God's love. When we love, we make the love that God has shown us to come to fruition in us. God's love transforms us into conduits of love, and if we are open to that transformation, we cannot help but love in return. Because Jesus allowed himself to be transformed by the Father's love, he was able to successfully fulfill his salvific mission. His Most Sacred Heart is a symbol of his willingness to love totally and in a selfless manner. It was not the hate of those who wanted him dead that led to Jesus' heart being pierced as he hung on the cross. Rather, it was the love that he had for his brothers and sisters that led to his death on the cross. Jesus was not dragged to the cross. He willingly gave himself for the life of the world.