A fool's tongue runs before his wit

मूर्खस्य पञ्च चिह्नानि
गर्वो दुर्वचनं तथा ।
क्रोधश्च दृढवादश्च
परवाक्येष्वनादरः ॥

A fool has five characteristic qualities; vanity, bad-mouthing, anger, stubbornness, lack of respect for others' opinions.

A fool's tongue runs before his wit.