This is the way it always was: a cloud by day and a fire at night. Horav Shlomo Yosef Zevin, zl, says this is a foreshadowing of our future: a cloud by day and a fire at night. When man is doing well, when his success is encouraging, the sun shines brilliantly before him. At such a time, he must remember that it is not always going to be like this. There will be times when the cloud will cover the sunshine, and the radiance will not penetrate. Conversely, he who is plagued with suffering, overcome with pain and affliction, should reflect upon the good times. He should never give up. Even in his darkest hour the fire will burn brightly, lighting up his life. He must have faith in the Almighty.
The Krias Shema of the morning and the evening are similar. In the morning, when the sun is shining and life seems to be idyllic, remember, “Hashem Elokeinu Hashem echad.” He gives strength – whatever success you enjoy is His gift which He can take back at any time if you do not use it properly. In the evening, we recite Krias Shema to affirm our faith in Hashem during periods of darkness, that the grief to which Hashem subjects us is l’tov, for the good.
The Mishkan was an edifice, but it was to be a part of every person. It was to reside in the heart of every Jew. The lesson of the fire and the cloud was to imbue Klal Yisrael with faith in the Almighty that times may change, but Hashem is always present.
Horav Mordechai Rogov,zl, explains that this is the reason that during the Pesach Seder, we refer to the Marror after the Korban Pesach and the Matzoh. One would think that we address the affliction prior to discussing our freedom from bondage. The Marror, symbolizing the bitterness of the slavery, should follow after Pesach and Matzoh, which signify our liberation. According to the above insight, we understand the importance of relating to the Marror during our liberation. We should remember the bitterness during our moments of joy, so that we will remember our joy during those moments when Hashem tests our faith.