What is the meaning of the glass of water with a botanica candle ritual?

I purchased a blue candle, oil and powder from a botanica to perform a healing ritual. I was told to put a picture of the person to be healed beneath the candle, write their name in the candle and sprinkle oil and powder into the candle. I was also told to place a glass of water next to the candle. What is the meaning of the glass of water?