Fast for one night is ordained for Vaishyas and Shudras. If they observe fasts for two or three nights by mistake, such fasts never bring on their advancement.
वैश्याः शूद्राश्च यन्मोहादुपवासं प्रचक्रिरे। त्रिरात्रं या द्विरात्रं वा तयोर्तुष्टिर्न विद्यते॥