Seven days. Why do we celebrate Chanukah for eight days?
The Taz (670:1) answer begins with a story from Navi (II Melachim 4). It states that a woman told Navi Elisha that she had debts, and the creditors threatened to take her two sons away as slaves. Elisha asked her בבית לך יש מה, "What do you have in your home?" She replied that she had some oil. Elisha said, "Borrow empty vessels from your neighbors and pour the oil into those vessels." Miraculously, the oil kept flowing until all the utensils were filled with oil. She was able to pay her debtors.
The Zohar explains that the miracle occurred solely because this woman had a drop of oil in her home. If she had nothing in her home, the brachah wouldn't come because "when nothing is there, the brachah will not come to create something new." If there is even a tiny drop, the brachah can increase it.
The Taz says that we now know that when the Kohanim lit the Menorah in the Beis HaMikdash on the 25th of Kislev, the oil wasn't entirely consumed. Some of the oil miraculously remained until the morning. We know this because the miracle wouldn't have occurred the next night if all the oil had been consumed on the first night.
The Taz writes, "In retrospect, they realized that a miracle happened on the first night. Had the oil been completely consumed on the first night, there couldn't have been a miracle the next night. Certainly, some oil [miraculously] remained from the first night. The brachah came upon that remaining oil. So, we see that there was a miracle on the first night, too."
Reb Aryeh Leib zt'l, the Maharal Tzinz ('ז לחנוכה דרוש ,למנחה קומץ) explains the Taz with a mashal:
Someone had ten crates filled with gold coins. Nine crates were stolen, and one wasn’t. Using the gold coins in the tenth crate, he hired police to search for the nine stolen crates. He vowed that if the gold were found, he would give three gold coins from each box to tzedakah.
The crates were eventually found, and true to his promise, he gave a gabbai tzedakah 27 gold coins, three from each stolen box. However, the gabbai tzedakah requested another three gold coins, from the tenth crate. The man replied, “That crate wasn't stolen. My gratitude to Hashem is that He brought back the nine crates. Why must I thank Hashem for the tenth crate, which was never stolen?”
The gabbai tzedakah replied, “Had the tenth crate also been stolen, you wouldn’t have had any money to pay for the search. The fact that it wasn’t stolen is part of the miracle, and you should thank Hashem for that, too.”
On Chanukah, we praise Hashem for the menorah that lit seven days more than expected, and we also praise Hashem for the oil that was left over on the first night because, without that oil, the miracle couldn’t have occurred.
We learn from this to praise Hashem for all the miracles we receive, including those that prepare the path for other miracles.
We shouldn't solely praise Hashem for those times when we had serious problems, and Hashem miraculously and kindly saved us. We should also praise Hashem for all the good we have, the areas where there aren't any problems at all.
We have much to be grateful for, and Chanukah is a holiday to praise Hashem.
