When the parashah speaks about the thanks-offering (Lev. 7:12), the sages say in the Midrash Tanchuma, “In time to come all the sacrifices will be abolished, but the thanks-offering will never cease”.
The general view is that this indicates that a person must always feel thankful for the blessings of life.
A further rabbinic interpretation says that this specially applies to someone who has never committed a sin (if such a person actually exists!).
Why should he or she have a particular reason to bring a thanksoffering? Out of gratitude to God who has protected him/her from succumbing to sin.