Tosefta Pesachim 1:1
Before daybreak on the 14th of Nisan, one searches for hametz by the light of the candle. One does not search by the light of the sun and not by the light of the moon, rather by the light of the candle, because searching by candlelight is more than enough, even though it does not allow one to see everything. It is a reminder of the verse (Zephaniah 1:12), "At that time, I will search Jerusalem by candlelight." And it is said (Proverbs 20:27), "The soul of a person is the candle of the Lord, revealing all of his or her inmost parts."
The ancient rabbis specify that the search for leaven in our households be conducted by candlelight, knowing that by using such a poor source of light, the search will be less effective. Why do they do this? In part, they want to make the observance of Pesach easier on us. And in part, they want us to focus on the spiritual meaning of the search, not the practical. They equate our searching of our houses for leaven with God's searching of our souls to see what is hidden there. Before we can experience the Festival of Freedom, we need to search inside of us to see what is preventing us from being free. Are we stuck in the past? Are we consumed by disappointment at a world that does not conform to our expectations? Are we held back by cynicism and hopelessness? Are we finding ourselves complicit in causing others to be enslaved or oppressed? Before Pesach, we have the opportunity to search out the corners of our souls and fill them with divine light. When we can see what is hidden there, we can put ourselves on the path to true freedom this year.