(During ‘itikaaf and outside of ‘itikaaf) a person should speak for that which he needs for religious and worldly affairs as for pointless superfluous speech then there is no benefit in it from two angles:
1. The wasting of a persons time and busying him away from the remembrance of Allah.
2. It’s possible and refuge is sought with Allah, that the speech may be impermissible and his speech may nullify his actions, because he utters a statement which Allah is angered by. It is possible a person could nullify all of his actions and apostate from Islam (1), therefore speech can be dangerous for a person if he does not safeguard it, and there is no curing it except by ‘itikaaf because when a person isolates himself solely for the worship of Allah, he accustoms himself and trains himself upon little speech and upon the restraining of his tongue.
Ta’leeqaat ‘ala Mukhtasar Zaad al-Ma’aad pages 601-602
(1) On the authority of Abu Hurayrah (Allah be pleased with him) that he heard the Prophet (Peace and Blessings of Allah upon him) say,
‘Indeed a servant may utter a single word and because of it plummet into the Hellfire farther than the distance between the east and the west.’ Bukhari 6477 Muslim 2988