The Kitáb-i-Aqdas - The Most Holy Book
Index term: for performance of religious duties, under Maturity, age of
n10.
the Prayer for the Dead
The Prayer for the Dead (see Some Texts Supplementary to the Kitáb-i-Aqdas) is the only Bahá'í obligatory prayer which is to be recited in congregation; it is to be recited by one believer while all present stand in silence (see note 19). Bahá'u'lláh has clarified that the Prayer for the Dead is required only when the deceased is an adult (Q&A 70), that the recital should precede the interment of the deceased, and that there is no requirement to face the Qiblih when saying this prayer (Q&A 85).
Further details concerning the Prayer for the Dead are summarized in the Synopsis and Codification, section IV.A.13.-14.
n13.
We have commanded you to pray and fast from the beginning of maturity
Bahá'u'lláh defines the "age of maturity with respect to religious duties" as "fifteen for both men and women" (Q&A 20). For details of the period of fasting, see note 25.
n25.
We have enjoined upon you fasting during a brief period
Fasting and obligatory prayer constitute the two pillars that sustain the revealed Law of God. Bahá'u'lláh in one of His Tablets affirms that He has revealed the laws of obligatory prayer and fasting so that through them the believers may draw nigh unto God.
Shoghi Effendi indicates that the fasting period, which involves complete abstention from food and drink from sunrise till sunset, is

. . . essentially a period of meditation and prayer, of spiritual recuperation, during which the believer must strive to make the necessary readjustments in his inner life, and to refresh and reinvigorate the spiritual forces latent in his soul. Its significance and purpose are, therefore, fundamentally spiritual in character. Fasting is symbolic, and a reminder of abstinence from selfish and carnal desires.

Fasting is enjoined on all the believers once they attain the age of 15 and until they reach the age of 70 years.
A summary of the detailed provisions concerning the law of fasting and of the exemptions granted to certain categories of people is contained in the Synopsis and Codification, section IV.B.1.-6. For a discussion of the exemptions from fasting see notes 14, 20, 30 and 31.
The nineteen-day period of fasting coincides with the Bahá'í month of 'Alá', usually 2-20 March, immediately after the termination of the Intercalary Days (see notes 27 and 147), and is followed by the feast of Naw-Rúz (see note 26).
n149.
The Lord hath decreed that the dead should be interred in coffins
In the Bayán, the Báb prescribed that the deceased should be interred in a coffin made of crystal or polished stone. Shoghi Effendi, in a letter written on his behalf, explained that the significance of this provision was to show respect for the human body which "was once exalted by the immortal soul of man".
In brief, the Bahá'í law for the burial of the dead states that it is forbidden to carry the body for more than one hour's journey from the place of death; that the body should be wrapped in a shroud of silk or cotton, and on its finger should be placed a ring bearing the inscription "I came forth from God, and return unto Him, detached from all save Him, holding fast to His Name, the Merciful, the Compassionate"; and that the coffin should be of crystal, stone or hard fine wood. A specific Prayer for the Dead (see note 10) is ordained, to be said before interment. As affirmed by 'Abdu'l-Bahá and the Guardian, this law precludes cremation of the dead. The formal prayer and the ring are meant to be used for those who have attained the age of maturity, i.e. 15 years of age (Q&A 70).
With regard to the material from which the coffin is to be made, the spirit of the law is that coffins should be of as durable a material as possible. Hence, the Universal House of Justice has explained that, in addition to the materials specified in the Aqdas, there is no objection to using the hardest wood available or concrete for the casket. For the present, the Bahá'ís are left free to make their own choices in this matter.
q20.
 
Question: Concerning the age of maturity with respect to religious duties.
Answer: The age of maturity is fifteen for both men and women.
q70.
 
Question: Is the use of the burial ring enjoined exclusively for adults, or is it for minors as well?
Answer: It is for adults only. The Prayer for the Dead is likewise for adults.
q92.
 
Question: In a treatise in Persian on various questions, the age of maturity hath been set at fifteen; is marriage likewise conditional upon the reaching of maturity, or is it permissible before that time?
Answer: Since the consent of both parties is required in the Book of God, and since, before maturity, their consent or lack of it cannot be ascertained, marriage is therefore conditional upon reaching the age of maturity, and is not permissible before that time.