Bahá’u’lláh says there is a sign (from God) in every phenomenon: the sign of the intellect is contemplation and the sign of contemplation is silence, because it is impossible for a man to do two things at one time—he cannot both speak and meditate.
(‘Abdu’l-Bahá, Paris Talks, p. 174)

For the tongue is a smoldering fire, and excess of speech a deadly poison. Material fire consumeth the body, whereas the fire of the tongue devoureth both heart and soul. The force of the former lasteth but for a time, whilst the effects of the latter endureth a century.
(Bahá’u’lláh, Gleanings from the Writings of Bahá’u’lláh, p. 264)

Not everything that a man knoweth can be disclosed, nor can everything that he can disclose be regarded as timely, nor can every timely utterance be considered as suited to the capacity of those who hear it.’ Such is the consummate wisdom to be observed in thy pursuits. Be not oblivious thereof, if thou wishest to be a man of action under all conditions. First diagnose the disease and identify the malady, then prescribe the remedy, for such is the perfect method of the skilful physician.
(‘Abdu’l-Bahá, Selections from the Writings of ‘Abdu’l-Bahá, p. 268)

Second, thou shouldst never compare the words of thy Imams with the words of the people, for verily utterance is a manifestation of the reality of the one who uttereth, and a mirror that reflecteth that which is in his heart. Thus, just as their own being is a sure testimony for all the worlds and an indisputable sign from God, glorified be He, so are their words... which do not resemble the words of any other creatures. Their utterance, which is at once all-encompassing and all-perfect, is the proof of God unto the people... All existence is the outcome of one letter of their utterance... Thus the word of the Imam, peace be upon him, embraceth all things and streameth forth in all the worlds acording to the conditions of their inhabitants.
(The Bab, “Tafsir-i-Hadith-i-Man ‘Arafa Nafsah faqad ‘Arafa Rabba", the Commentary on the Tradition ‘He Hath Known God Who Hath Known Himself‘, Iran National Bahá’í Archives, 14:474 – 82).

Speech is a powerful phenomenon. Its freedom is both to be extolled and feared. It calls for an acute exercise of judgement, since both the limitation of speech and the excess of it can lead to dire consequences. Thus there exist in the system of Bahá’u’lláh checks and balances necessary to the beneficial uses of this freedom in the onward development of society. A careful examination of the principles of Bahá’í consultation and the formal and informal arrangements for employing them offer new insights into the dynamics of freedom of expression. As it is beyond the scope of this letter to expatiate upon these principles, let it suffice to recall briefly certain of the requisites of consultation, particularly for those who serve on Spiritual Assemblies. Love and harmony, purity of motive, humility and lowliness amongst the friends, patience and long-suffering in difficulties—these inform the attitude with which they proceed “with the utmost devotion, courtesy, dignity, care and moderation to express their views", each using “perfect liberty” both in so doing and in “unveiling the proof of his demonstration”. “If another contradicts him, he must not become excited because if there be no investigation or verification of questions and matters, the agreeable view will not be discovered neither understood.” “The shining spark of truth cometh forth only after the clash of differing opinions.” If unanimity is not subsequently achieved, decisions are arrived at by majority vote. Once a decision has been reached, all members of the consultative body, having had the opportunity fully to state their views, agree wholeheartedly to support the outcome. What if the minority view is right? “If they agree upon a subject,” ‘Abdu’l-Bahá has explained, “even though it be wrong, it is better than to disagree and be in the right, for this difference will produce the demolition of the divine foundation. Though one of the parties may be in the right and they disagree, that will be the cause of a thousand wrongs, but if they agree and both parties are in the wrong, as it is in unity, the truth will be revealed and the wrong made right.” Implicit in this approach to the social utility of thought is the profundity of the change in the standard of public discussion intended by Bahá’u’lláh for a mature society.
(The Universal House of Justice, 1988 Dec 29, Individual Rights and Freedoms, p. 7)