NUM204 R. Nathan said: There is not a single precept in the Torah whose reward is not enjoyed in this world. You may learn this from the mitzvah of tzitzit, which requires us to put tassels on the corners of any poncho-like garment. ... With regard to [the commandment of tzizit], the expression 'I am Adonai your God' is written twice [in this verse]. It means, I am He who will exact punishment in the future, and I am He who will give reward in the future. The tzizit appeared to me as four witnesses testifying against me. (From a story about a disciple of the sages who visits a harlot, recounted in Men. 44a).