The Baal Shem Tov taught that from everything that a Jew sees or hears he must take a lesson in his service of G-d. This teaching finds its roots in the words of the Talmud, "Of all that G-d created in His world, He did not create a single thing without purpose" (Shabbos 77b). Or, as the Mishna says in Avos (6:11), "Everything that G-d created in His world, He created only for His glory." Included in "everything that G-d created," taught the Baal Shem Tov, is your encounter with any particular object or situation; your very perception of it was created for a purpose that will bring about "G-d's glory." G-d orchestrated your encounter with this article or event in order for you to apply its message in your duties toward G-d.
This idea is hinted in Rashi's commentary on the verse, "You shall not stand by the blood of your neighbor," which means, in Rashi's words, "to see his death and you are able to save him." Rashi does not write the final clause tentatively, "if you are able to save him", but factually, "and you are able to save him." Rashi's words thus imply that your awareness of your friend's suffering is in and of itself an indication that you are able to save him! And the proof is obvious: otherwise, why would your friend's suffering be made known to you "without purpose"?
The same principle applies equally when your fellow is at risk of spiritual death, as unfortunately so many of our Jewish brothers and sisters are today. The Torah warns us that we may not stand idly by our brothers' blood. Our very awareness of the spiritual threat facing our fellow Jews indicates that we are capable and personally obligated to save them, by each of us taking active part in the dissemination of Torah and Judaism.
—Likutei Sichos vol. 32, pp. 125-126