Among all the important Smritis, Katyayana Smriti is one which discusses things related to religious doctrines and policy and also pacifying deceased ancestors, the method of performing Yagya, Havanna Yagya and the other rituals related to religious activities.
Katyayana has classified the entire Smriti into 29 sections i.e.
1) Description of conduct.
2) Rituals to pacify deceased ancestors.
3) Description of Trividha Kriya.
4) Pacifying deceased ancestors.
5) Repetition of the method of pacifying deceased ancestors.
6) Other Karmas (rituals).
7) Description of the pipal tree.
8) The method of kindling the Yagya fire.
9) Description of the ways to perform Yagya from dawn to dusk.
10) The morning ablutions i.e. holy bath etc.
11) Method of doing Sandhya.
12) The method to pacify deceased ancestors.
13) Method of performing Panchamaha Yagya.
14) Method of performing Brahma Yagya.
15) Method of executing Yagya.
16) Determining auspicious time to please deceased ancestors.
17) Repetition of the method to pacify deceased ancestors.
18) Method of kindling the altar for marriage ceremony.
19) The duties of a woman.
20) The Vedic method of kindling the altar for the second marriage.
21) Rituals for performing last rites.
22) Rituals for holy bath after performing last rites.
23) Rituals for performing last rites of the person who died unnaturally.
24) Daily ablutions for cleanliness/purification.
25) Repentance for partaking food without Yagya.
26) Nava Yagya Execution. (cows, bull, horse etc)
27) Method of repentance.
28) The duty of the Brahmin and the fruits he begets thereof.
29) Repetition of the method of pacifying deceased ancestors.
According to Katyayana, the Agnihotri (one who enkindles the Yagya), is the one who leads an ideal life. The purview of the authority and right of women in the Yagya has also been discussed comprehensively by Katyayana. Katyayana opines that without a wife the Yagya is incomplete.
The author of this Smriti says that if the wife expires and the man has not got a second wife, a small idol of a woman, made of Kusha (grass) or an alloy, should accompany the man during the rituals.
Katyayana says that the woman can participate in the Ardhangini Yagya also. Her presence for a yagya is imperative. The making of a golden idol of Seeta by Lord Rama during the Ashwamedha Yagya espouses the cause.
Katyayana says that person who does not allow his wife to participate in the Yagya becomes a woman in the next birth and the woman becomes a man. The Acharya supports women and states that only one wife (woman) is authorized to participate in such an important action like Yagya.
Performing of the Yagya along with another woman while the first legitimate wife is alive, is like committing a murder.
Katyayana espoused the cause of woman to such a great extent that he allowed even those women to participate in a Yagya, who have certain physical flaws and demerits. He says that if the woman is not allowed to participate in the Yagya during her life and she expires as such, then for the next three lives, the husband takes birth as the woman and the woman takes birth as the man.
Katyayana says that a person does not beget fruits of the actions performed if he has not worn the thread and has not kept a strand of hair left on the tonsured head (Shikha)
Before beginning any worship, the worship of Ganesha and Matruka is imperative says Katyayana.
KARMADISHU TU SARVESU MATARAHA ||
SAGANADHIPA PUJANIYAAHAA PRAYATNENA PUJITAHA PUJAYANTI TAAHA ||
Meaning : Before the beginning of the Yagya the worship of Lord Ganesha and sixteen Matrukas should be performed. One begets everything if he performs the worship properly. It can be inferred that the Katyayana Smriti is beneficial to one and all in the Kali Yuga. These fundamental policies have left considerable influence on all the eras.