Lighting the Yahrzeit candle is probably the most well-known of Yahrzeit customs. The candle is lit at sundown on the eve of the anniversary of the passing and the candle should remain alight for twenty-four hours. The flame of a candle is compared to a soul. Just as a flame is never still, so too does the soul continuously strive to 'reach up' to G-d. Also, just like the human soul, the flame of the candle is something that you cannot touch and has no corporeal quality, but nevertheless you know that it is there. Watching the flickering flame one is easily led into introspection and thoughts of the departed soul.

The connection between the flame and a candle derives from the Book of Proverbs (chapter 20, verse 27): "The soul of man is the light of God."