In Jain Dharma, maintaining purity and cleanliness in food is important. Regarding milk kept overnight:

• Do not keep milk at room temperature overnight. In warm climates it can quickly sour and become unsuitable for consumption.
• The safer practice is to refrigerate milk as soon as possible in a clean, covered container.
• If you refrigerate boiled milk, it can stay usable for about 1–2 days. Before use, you may reheat it gently to ensure it’s fresh tasting.
• If milk has been left out for several hours or shows any sour smell, curdling, or off taste, it should be discarded to avoid consuming spoiled dairy.

Simple guidelines:

• Store milk in a clean bottle, tightly closed.
• Refrigerate promptly; don’t leave it out overnight.
• When in doubt about freshness, err on the side of caution and discard.

If you’d like, I can tailor these guidelines to your climate and typical storage conditions.