The Kitáb-i-Aqdas - The Most Holy Book
Index term: questioning, under He Whom God shall make manifest
k126.
In the Bayán it had been forbidden you to ask Us questions. The Lord hath now relieved you of this prohibition, that ye may be free to ask what you need to ask, but not such idle questions as those on which the men of former times were wont to dwell. Fear God, and be ye of the righteous! Ask ye that which shall be of profit to you in the Cause of God and His dominion, for the portals of His tender compassion have been opened before all who dwell in heaven and on earth.
n146.
In the Bayán it had been forbidden you to ask Us questions.
The Báb forbade His followers to ask questions of Him Whom God will make manifest (Bahá'u'lláh), unless their questions were submitted in writing and pertained to subjects worthy of His lofty station. See Selections from the Writings of the Báb.
Bahá'u'lláh removes this prohibition of the Báb. He invites the believers to ask such questions as they "need to ask", and He cautions them to refrain from posing "idle questions" of the kind which preoccupied "the men of former times".