Warmth of Service
Said the Riziner: "I will illustrate to you the necessity of warmth in the service of the Lord. The Torah (Leviticus 15:13) bids us when we become unclean to immerse ourselves in water and thereby be purified. But if the water is frozen, can we immerse ourselves in it? A frozen heart canot purify an unclean life."
Source: Beth Phineas