It has been related in some books that Nabi Yakoob (a.s) once was visited by a beggar on a Friday night. Although Nabi Yakoob heard the beggar, he didn't feed him.

In order to make Nabi Yakoob realize the importance of charity, Allah (swt) revealed to him that due to this act Allah would soon put Nabi Yakoob to a test, and that he should show patience in face of this test.

After that Nabi Yakoob was tested by the temporary loss of Nabi Yusuf, his son, for quite a long period. Due to this Nabi Yakoob really suffered, until he finally was reunited with his son. (KALIMATULLAH BY SHAHEED HASSAN SHIRAZI PAGE 202)