If you are sitting among a group of people, it is better that [those people] say to you, “Speak! Why are you so quiet?”, than if you were to speak, and your words would be a burden to them, and they would say to you, “quiet”.
[Furthermore], it is written [in Michah (7; 5)]: “From the one that dwells in your chest, guard the openings of your mouth.” [This] pasuk hints to us, that the mouth is similar to a doorway, and just as the doorway of the house has a time to be opened and a time to be closed, for if it would always be opened, all that is in the house would be destroyed. So too, this is the case with the opening of the mouth, there is a time to open them [to speak] words of Torah and [of] other necessary things, and there is a time to close them, [to refrain from speaking of] the other [types of speech].
A person [must also] be aware that the [ability of] speech is the most loved of all of the loved [abilities], for through this [ability], the form of the person is completed.
Therefore, just as a person who possesses gold, silver, and pearls, makes an enclosure for an enclosure to guard them and he conceals these [treasures] in his inner-chamber, inside a box designated for this, similarly, to a greater degree than this, a person must make an enclosure for an enclosure for his mouth, that being in [the enclosure of the attribute of] silence, as mentioned earlier.
 The passage in the gemara states as follows, “The [attribute of] silence is appropriate for the Torah scholars, how much so, [it is appropriate] for the fools, as it says, “Also a fool who is silent will be considered [to be] a wise man, [if he seals his lips, [he will be considered to be] a person of understanding.]” (Mishlei: 17; 28)”
The preceding pasuk states, “One who prevents himself from making [vain] statements, is knowledgeable, one [who treats his words as carrying] value, is a man of understanding.” (Mishlei: 17; 27)
The above translation is based on Metzudas David. Onkelos translates the pasuk as “…one who is humble is a man of understanding.”
Metzudas David has a varying understanding on the pasuk quoted in the gemara, where he explains that the individual who silences the fool is considered to be wise, while one who prevents the fool from saying that which he wishes, is considered to be an individual of understanding.
On these pisukim, the RaLBa”G explains that the person who is knowledgeable prevents himself from speaking unless he has to say something of necessity. The individual who is understanding treats himself with value, not joining up with individuals of “stature” and he will [try to] avoid excessive speech. Of course, none of the above is done through a sense of haughtiness. By acting in such a manner, the individual will benefit, as, by preventing himself from speaking excessively, his foolishness will leave him, and he will also be considered to be an understanding individual if he seals his lips and does not speak at all.
 Bartenura explains that this Mishna is teaching that one should avoid speaking that which is unnecessary and should limit his speech as much as possible.
 The RaLBa”G explains that the words of the fool present himself with a self-inflicted danger, for, by opening his mouth, he may come to incite a quarrel and he may open his mouth to try to defend his fellow, and, in the process, reveal information that was meant to have been kept secret, leading to discontent.
The MaLBI”M explains that the fool, with his lips, will ensnare his soul and through the words of his mouth, he will bring destruction upon himself. By opening his lips [to speak that which is forbidden, he could] ensnare his soul in the pit of destruction, and through that which he speaks with his mouth, he also brings destruction to his body, for, [through this forbidden speech], HaShem [may] bring bodily punishment upon the individual.
 The teachings, beginning with the words, “He who is accustomed in [the attribute] of silence” – beginning of the 19th of Kislev, up to this point – are copied from sefer “Orchos Tzaddikim”, “The Gate of Silence”, see over there [for more on the importance of the attribute of silence].
 The translation of "פתחי" – “pischei” is “openings” or doorways”.
The entire pasuk reads as follows:
“Do not [put your] belief in your fellow, do not trust in the leader. From the one that dwells in your chest, guard the openings of your mouth.” (Mishlei: 7; 5)
RaSh”I comments that the one who “dwells in your chest” refers to your soul, which will testify against you [regarding your actions and words before the Heavenly tribunal]. Metzudas David and RaDa”K explain that the one who “dwells in your chest” refers to your wife. Do not [even] reveal to your wife information that is meant to be kept secret, for the information is bound to be revealed. RaDa”K explains that one should not speak negatively about his fellow to his wife.
Clearly, if one is to not reveal such forbidden speech to one’s wife, to whom he confides, how much more so should he similarly be careful to not speak these forbidden words to other people.