Hashem told Avrohom that his children would be enslaved in Mitzrayim for 400 years. Yet they left after 210. Many Meforshim offer explanations justifying how Bnei Yisrael were able to leave before their time. However, the Ben Ish Chai has a problem with this whole approach. When they left Mitzrayim the Pasuk says (Bo 12:42), “Leil Shimurim Hu Lashem L’Hotzium MeiEretz Mitzrayim; This was the night that Hashem waited for as they were destined to leave Mitzrayim.” This implies that they were always scheduled to leave Mitzrayim on this night even though it was not yet 400 years.
The Ben Ish Chai explains with a Mashal. A father tells his son he must empty out an entire warehouse from the junk that has been accruing there. He tells him he has the whole night and it must be done by daybreak. The father knows that this is an impossible task to accomplish so in the dark of the night as the son is working with all his effort, the father goes in and helps him. The son comes to the father proudly in the morning, telling him the job is done. He has no idea that his father did most of the heavy lifting for him.
The four hundred years in Mitzrayim was the workload Hashem gave Bnei Yisrael to be Misaken what needed to be fixed and to be mivarer the nitzotzos that were trapped in the galus of Mitzrayim. Although there was 400 years of work there, Hashem set a deadline to take them out on the night of Pesach. How did they manage? They did their best, and Hashem in His compassion did the rest for us by shining His Shechina.
This is a lesson for all generations as the end of the pasuk says, “Shimurim L’Chol Bnei Yisrael L’Dorosam; In every generation Hashem gives us a job.” We struggle to survive each Galus and be Mikadesh Shem Shamayim. If we give 100% effort and try to accomplish the impossible, Hashem will do the rest, just like He did in Mitzrayim.