Reciprocity, according to the Oxford Dictionary, is the practice of exchanging things with others for mutual benefit, especially privileges granted by one country or organization to another. In all my years of studying and teaching the Catholic faith, reciprocity is a simple way of explaining the covenant we have with God since the beginning.
God told Abraham that should Abraham know, love and serve the one true God, then his descendants would number the stars. Additionally, God says that the descendants of Abraham will always be provided for with land, children, and security with the understanding that they continue to come to know, love and serve the one true God as well.
Now, as you watch the Old Testament unfold, we see our ancestors in faith struggle with keeping their end of the bargain. It is the human condition. We fall into and out of relationship with God (sin) but God always remains and patiently waits for us to unite with Him - this is faith.
The greatest calls to faith always encompasses a tragic event. The Hebrews called out to God when enslaved in Egypt. They called out when enslaved in Babylon. The Israelites called out when under the thumb of the Roman Empire. It is no different in modern times. Many churches saw filled seats the days, weeks and months following 9/11, only to find them emptying again.
Jesus reclaims and invigorates the reciprocity that exists between humanity and God, the Father and Creator - "I am the bread of life... whoever eats this bread will live forever" (John 6: 48-51). Just as faith in God saved our ancestors, faith in Jesus Christ saves us.
Reciprocity. Don't wait for the next tragic event to get you back into relationship with Jesus. Be there before it happens.