Rav Dov Yaffe Shlit"a, who is a Mashgi'ah at various Yeshivot in Israel, said the following essay, which was then put to writing by his students in a pamphlet entitled "Vetaher Libenu" - לקט עצות והדרכות בעניני טהרת העינים קדושת הגוף ועוד. The following is an excerpt (my translation):
The Final Birur
Not everyone will merit to see the coming of the Mashiah
I want to say something very critical! We are so much anticipating the coming of the Mashiah, but you need to know that not everyone will merit! And just like during the Exodus, not everyone left, similarly, during the coming of the Mashiah, those that are drawn after impurity will not merit to see the coming of the Mashiah...!!!
The critical test
Man sets his fate whether when Mashiah comes, he will be one of the fortunate ones or one of the unlucky ones Has Veshalom. And since we are close to the coming of the Mashiah, therefore, HKB"H gave the Sitra Ahara permission to test us and to select who indeed is serving Hashem honestly. It is very important that we do not forget this - that right now is the final Birur (selection): Who is to Hashem and who Has Veshalom is not? Therefore, it is so especially important right now to be careful not to leave the Camp of the Shechina because one who is not careful and is not paying attention could Has Veshalom lose his entire [portion in the next] world...!!!
"On the doorway of Gehinnom"
We see a scary thing - that nowadays, it is much easier to falter than in the past, since then, if someone wanted to Has Veshalom sin, he had to stay far away alone, whereas today, it is possible with a small device that can be found in the pocket to watch all the abominations of the world, Rahmana Litzlan, and by doing so, a man can find himself at the opening of Gehinnom... and lose his entire [portion in the next] world, Rahmana Litzlan. Therefore, we need to be careful using an "extra distance" from such things!!!
"Whoever is on Hashem's side, come to me"
The idea that HKB"H gave the Sitra Ahara permission to test us so much is not a coincidence - this is the strong test and selection before the coming of Mashiah to check and clarify who is for Hashem and who is Has Veshalom for the Sitra Ahara. Unfortunately, we already heard hair-raising stories about men and women - and even from honorable families - who have faltered in this terrible thing - Hashem should guard us. Therefore, we need to very much stand on guard!
And choose life
It says in the Torah
, "Behold, I am setting before you life... and death". And the question is: which will man choose - HKB"H or the Sitra Ahara? Life or death? And this is not a simple question of whether he is doing something improper or if he had faltered or not. Rather, the question is to which camp you belong - to the Camp of the Shechina or to the Camp of Impurity, Rahmana Litzlan. And when the man goes to look at this device, it is considered as if he's choosing the latter... and according to what we said, he will not merit to the coming of the Mashiah and the like.
One who comes to purify oneself...
And fortunate for us that we are promised that one who comes to purify oneself receives [Heavenly] assistance, but one should remember that also one who comes to make oneself impure has doors opened for him! And one should pay attention that the Yetzer Hara is ensnaring us and wants to kill us. And Baruch Hashem that we are promised that even if one merely "comes" to purify oneself, already Heaven is helping him out.
To withstand the test
These are very critical things, and one who falters in this Has Veshalom, it will be very difficult afterwards to get out of it. And we must learn from Yosef Hatzadik, who, over all the impurities of Egypt, withstood the test and remained righteous. And without a doubt, we will be able to withstand these tests!