The Book of Prohibited actions

Riyad as-Salihin, The Book of the Prohibited actions
Book 18, Hadith 1511
Narrated 'Abu Hurairah (ra):
The Prophet (pbuh) said, "He who believes in Allah and the Last Day must either speak good or remain silent."[Muslim].

Riyad as-Salihin, The Book of the Prohibited actions
Book 18, Hadith 1512
Narrated 'Abu Musa Al-Ash'ari (ra):
I asked the Messenger of Allah (pbuh): "Who is the most excellent among the Muslims?" He said, "One from whose tongue and hands the other Muslims are secure."[Al-Bukhari and Muslim].

Riyad as-Salihin, The Book of the Prohibited actions
Book 18, Hadith 1513
Narrated 'Sahl bin Sa'd (ra):
The Messenger of Allah (pbuh) said, "Whosoever gives me a guarantee to safeguard what is between his jaws and what is between his legs, I shall guarantee him Jannah."[Al-Bukhari].

Riyad as-Salihin, The Book of the Prohibited actions
Book 18, Hadith 1514
Narrated 'Abu Hurairah (ra):
I heard the Prophet (pbuh) saying, "A person utters a word thoughtlessly (i.e., without thinking about its being good or not) and, as a result of this, he will fall down into the fire of Hell deeper than the distance between the east and the west."[Al-Bukhari and Muslim].