The Rebbe expresses joy at hearing about a recent farbrengen and uses the recipient’s new business — sterilizing used bags — as a parable: just as heat removes bacteria from bags, immersing in Torah and Chassidus purifies a person from negative influences. He blesses him with success materially and spiritually.
https://www.torahrecordings.com/rebbe/004_igros_kodesh/iyar/1027