This is Jesus's response when Peter asks him if we are supposed to forgive someone who errs against us. More about the terms used in the previous verse as "forgive" and "sin" in this article. So the question to Jesus was. how often do we let the mistakes of others go?
The hidden significance of this verse is that our idea of the number seven being lucky comes from Jewish tradition. Using the Jewish method of converting words to numbers, (gematria), the most common word for luck converts to seven and another word for luck converts to seventy-seven.
Christ's Words in Matthew as a Guide to 40 Days of Prayer.