ויאמר ה' אל משה הנך שוכב עם אבותיך וקם העם הזה וזנה אחרי אלהי נכר הארץ... ועזבני והפר בריתי... וחרה אפי בו... ועזבתים והסתרתי פני מהם והיה לאוכל ומצאהו רעות רבות וצרות. ואומר ביום ההוא הלא על כי אין אלוקי בקרבי מצאוני הרעות האלה, ואנכי הסתר אסתיר פני ביום ההוא
17 Then My anger shall be kindled against them on that day, and I will forsake them, and I will hide My face from them, and they shall be devoured, and many evils and troubles shall come upon them; so that they will say on that day, "Are not these evils come upon us because our God is not among us?" 18 And I will surely hide My face on that day for all the evil which they shall have wrought, in that they are turned unto other gods. (Translation from Mechon Mamre)
(דברים ל"א, ט"ז-י"ח)
Why is the lashon of the double language (הסתר אסתיר) changed? It should be identical אסתר אסתיר
or הסתר הסתיר. I saw the reason in Sefer Peninim Meshulchan Hagra: On that day Hashem will make hidden (הסתר) the fact that He is being hidden (אסתיר). All our sorrow, pains and sufferings come as a result of Hashem being אסתיר. If we realized this then we would quickly make Teshuva and be rescued from our sufferings and difficult situations. But Hashem makes this path hidden from us. Instead of attributing the situations we are put in to Hashem (sending us a message) we attribute them to טבע and as a result fail to do Teshuva and our Yisurin don't achieve their purpose. In fact, the gematria of הטבע is the same as אלהים — the One we need to attribute everything to. I saw in Sefer Orchot Tsadikim and in Derec Hashem that one who fails to do Teshuva as a result of his Yisurin will not be atoned for from those yisurin and his punishment will be doubled — he will have to endure more suffering until he realizes that he needs to do Teshuva. In fact Hashem many times sends a person yisurin just so he can do Teshuva. If he does Teshuva then those Yisurin will achieve their purpose and also atone for his sins. Therefore, a person can avoid a fair amount of suffering by doing Teshuva for his sins right away and accepting upon himself עול מלכות שמים.
According to the Zohar the number 16 represents Hashem's sword (the blade is a vav and the shaft is a yud). With this sword Hashem defeats our enemies. It is fair to assume that He also chastises us with this sword as a loving Father chastises his beloved son. If you look at the letters that differ/(are) additional (from the root סתר) in the words הסתר אסתיר you will notice a heh (5) + alef (1) + yud (10)= 16. So behind the scenes Hashem is chastising us with His sword but we fail to realize this and instead we attribute our difficulties to nature. The reason we make this mistake is because Hashem is making His Hester Panim hidden from us. Unfortunately, this is very prevalent in today's age where people are ignorant and are caught up in the natural flow of the world to the extent where they fail to notice their purpose for existence and subtract the רבונו של עולם from the picture ח״ו. People go through much anxiety and distress because of pain and difficult situations and are like blind people who can't be cured because they can't recognize the remedy (Teshuva).
In Tefila we make a point to illustrate that the relationship we have with Hakadosh Baruch Hu is anything but bound by nature. We say רופא חולי עמו ישראל in the blessing for healing. Why don't we say רופא אדם? Because the healing that Hashem does for the Jewish nation is different than the healing for goyim. We are not bound to natural means, Hashem performs the supernatural for us. This is evidenced in many stories of miraculous recoveries that were accomplished through Tefilah and mitsvot — some cases where the doctors become religious as a result of the open miracle. Hashem has given us a special gift — to cry our eyes out in Tefila for forgiveness and to be saved from the yester hara. If we were to realize the precious relationship that we have with Hashem and that He has the ability to provide for us in the supernatural then we would never veer off the path of Torah and mitsvot and we would live lives free of anxiety and stress. But since Emuna is something that needs constant chizuk it is up to us to learn mussar and strengthen our Emuna and Bitachon in Hashem so we can be Dovek to Hashem and see the supernatural and the coming of Moshiac soon in our days, Amen!