I hope you wouldn't mind me adding to your list of quotes something from
St John Climacus' Ladder of Divine Ascent. He has a chapter on silence, which is aptly short and therefore easy to quote in its entirety:
1. In the preceding chapter we spoke briefly of how extremely dangerous it is to judge others or rather to be judged and punished by one’s own tongue and of how this vice steals into even the most apparently spiritual people. Now we must show the cause of this vice, and give a proper account of the door by which it enters, or rather, goes out.
2. Talkativeness is the throne of vainglory on which it loves to show itself and make a display. Talkativeness is a sign of ignorance, a door to slander, a guide to jesting, a servant of falsehood, the ruin of compunction, a creator of despondency, a precursor of sleep, the dissipation of recollection, the abolition of watchfulness, the cooling of ardor, the darkening of prayer.
3. Deliberate silence is the mother of prayer, a recall from captivity, preservation of fire, an overseer of thoughts, a watch against enemies, a prison of mourning, a friend of tears, effective remembrance of death, a depicter of punishment, a delver into judgment, a minister of godly sorrow, an enemy of freedom of speech, a companion of stillness, an opponent of desire to teach, increase of knowledge, a creator of contemplation, unseen progress, secret ascent.
4. He who has become aware of his sins has controlled his tongue, but a talkative person has not yet got to know himself as he should.
5. The friend of silence draws near to God, and by secretly conversing with Him, is enlightened by God.
6. The silence of Jesus put Pilate to shame, and by a man’s stillness vainglory is vanquished.
7. Peter, having said a word, lamented it bitterly, because he forgot him who said: ‘I said, I will take heed to my ways that I sin not with my tongue,' and the other who said: ‘A fall from a height to the ground is better than a slip with the tongue.’
8. I do not wish to write much about this, even though the wiles of the passions urge me to do so. But I once heard from someone who asked me about silence that talkativeness is invariably born of one of the following causes: either from a bad, lax environment and habit (for the tongue, said he, being a member of the body, like the rest of the members, requires the training of habit), or again, in the case of ascetics, garrulity comes especially from vainglory, and sometimes also from gluttony. That is why many who bridle the stomach by force afterwards easily check the tongue and its chatter.
9. He who is anxious about his departure, cuts down words; and he who has obtained spiritual mourning, shuns talkativeness like fire.
10. He who has come to love silence shuts his mouth, but he who delights in wandering about outside is driven out of his cell by his passion.
11. He who knows the fragrance of the Fire from on high, runs from a concourse of men like a bee from smoke; for the bee is routed by smoke, whereas man is hampered by company.
12. Few can hold water without a dike; still fewer can tame an intemperate mouth.
The eleventh step. He who has mastered it has cut off at one blow a multitude of evils.
