The meaning of Chelleh Neshini (worshipping for a forty day period) in the field of spiritual wayfaring is for one to be watchful over oneself for a period of forty days, in order that through these means, he can obtain the necessary preparation and capacity to receive divine wisdom.
The reason behind the number forty in this practice is due to the special mystery and meaning given to the number; within this period, certain hidden capabilities and aptitudes reach perfection and completion. It is mentioned that human beings reach full mental perfection and completion at the age of 40:
His mother carried him with difficulty, and delivered him with difficulty. His bearing and weaning takes thirty months. Until, when he has attained his maturity, and has reached forty years, he says, “Lord, enable me to appreciate the blessings You have bestowed upon me and upon my parents, and to act with righteousness, pleasing You. 1
The forty day period of worship has also been described in the Quran in the place where God gave a promise to Prophet Moses (a) and took him to his Miqat (rendezvous) in a period of forty days:
And We appointed to Moses thirty nights, and completed them with ten; and thus the time appointed by his Lord was forty nights. 2
This brand of worship and careful watch has been given special attention by those after spiritual wayfaring, and it has also been emphasized in the traditions. Amongst these traditions, we find the following:
Whoever keeps himself pure for forty days for the sake of Allah, the currents of wisdom will open from his heart to his tongue. 3
Another tradition from Imam Baqir (a) mentions:
No servant will remain sincere in his faith of God for forty days, but that the lord will make him less attentive of this world, and He will show him its ‘ailments’ and ‘remedies’. Then, wisdom will take root in his heart and his tongue will become capable of elucidating this wisdom. 4
Naturally, as have been taught to us through religious teachings, these actions are required throughout all of one’s life, and this recommendation of a forty day period is only there as a means of spiritual practice and training for making it a continuous part of one’s life.
The Urafa, in order to maintain the necessary watchfulness for the period of forty days and nights, have recommended certain specific actions. Overall they contain instructions in caution during the course of eating, sleeping, and speaking; the spiritual wayfarer must strive during this period in engaging himself in continuous remembrance of God and his worship. Naturally, as have been taught to us through religious teachings, these actions are required throughout all of one’s life, and this recommendation of a forty day period is only there as a means of spiritual practice and training for making it a continuous part of one’s life. Sometimes, it is imagined that this forty day period necessitates seclusion from the society and that the spiritual wayfarer must busy himself in the worship of God somewhere far away from the people; we must mention that such a thing is not necessary, and in fact, if a spiritual wayfarer is able to engage in his worship while participating in his society and community, then of certainty, this contains a much greater reaction and result for himself. A great number of the Shia Urafa and scholars have given emphasis to the worship of forty days and they have naturally practiced it themselves; as an example, we can look at Seyed Bahr al-Ulum and both the first and the second Majlisis:
In the book spiritual wayfaring, which has been attributed to Bahr al-Ulum , the following has been mentioned:
“The effect the forty days has on the actuality of one’s potentials, and on the instilment of qualities is something explicitly mentioned in Quranic verses and hadiths, and something experienced by the elite”. 
Similarly, Mulla Muhammad TaqiMajlisi has written in regards to the worship of forty days:
One of his complaints is that the worship of forty days is a religious deviation, but this is not the case. A religious deviation is that which was previously mentioned and there are a great many traditions in regards to the virtue of the worship of forty days. 
It must be mentioned that the Urafa have emphasized that this form of worship should never take on the form of seclusion or isolation from society. In the matter of the Chelleh Neshini, the Urafa have mainly emphasized a form of watching over one’s inner self and a form of isolation in regards to one’s own heart (inner self), but they have not recommended isolation from ones society and community.
Therefore, worshipping God and having purity in intention while serving him during this period of forty days is counted as one of the best forms of worship. At the same time, it must be mentioned that the Urafa have emphasized that this form of worship should never take on the form of seclusion or isolation from society. In the matter of the Chelleh Neshini, the Urafa have mainly emphasized a form of watching over one’s inner self and a form of isolation in regards to one’s own heart (inner self), but they have not recommended isolation from ones society and community.