What is a common central message shared by Night, "The Perils of Indifference," and "A God who Remembers"?

The central message shared by all three is this: indifference allows evil to triumph, but indifference can be overcome through the sharing of memories.
Through his writing and speeches, Elie Wiesel shared his experience of the Holocaust. At the end of Night, we read Wiesel's acceptance speech at his Nobel Peace Prize ceremony on December 10, 1986.
In that speech, Wiesel warns against indifference. He argues that "neutrality" is nothing more than indifference. In turn, this indifference aids the tormentor at the expense of the victim. Wiesel maintains that wherever human lives are endangered, human dignity hangs in the balance. At such a time, "national borders and sensitivities" should be irrelevant. Instead, concerned parties ought to rise up against injustice. There is no other recourse for a civilization that will endure.
In writing Night, Wiesel chose to share his memories of Buchenwald and the terrible concentration camps. In sharing, he hoped to inflict a deathblow on indifference. According to Wiesel, the world should never forget what the Jews suffered, lest history be repeated. Wiesel made the same point in "A God Who Remembers" and "The Perils of Indifference."
In "A God Who Remembers," Wiesel argues that all experiences should be shared (whether negative or positive). By sharing memories, one also shares information. By extension, this information inspires sensitivity to human suffering and ultimately results in an increased commitment to justice. Justice then ensures the survival of mankind.

Without memory, there is no culture. Without memory, there would be no civilization, no society, no future.

Wiesel emphasizes this point in "The Perils of Indifference." In that speech, he charges that indifference is detrimental to the survival of mankind. To share is to honor the dead, as well as the living.

For the survivor who chooses to testify, it is clear: his duty is to bear witness for the dead and for the living. He has no right to deprive future generations of a past that belongs to our collective memory. To forget would be not only dangerous but offensive; to forget the dead would be akin to killing them a second time.