Before showing the conditions required in the na'ib and the one who hired him we may mention some areas in which istinabah and willing Hajj could be applied and the related rules:

40. If Hajj becomes wajib on somebody and due to old age, sickness or extraordinary hardship, which may result, he could not perform it and he becomes hopeless of doing it, even in the following years, without extraordinary hardship, then istinabah becomes wajib on him. While that on whom Hajj is not wajib, istinabah is not wajib on him.
    
41. When the na'ib performs Hajj, the excused hiring person would be free of the obligation of Hajj, and he does not have to repeat Hajj himself even if the excuse is removed later. However, if the excuse is removed during the na'ib's Hajj, the one who hired him should repeat the Hajj because the Hajj of the na'ib, would not be valid.
    
42. If one, on whom Hajj is already settled, dies during the way, then if he dies after ihram and entrance of the Haram, this Hajj would be valid in the place of Hajjat al-Islam. While if death happens before ihram, then it is not valid. For someone who dies after ihram and before entering the Haram, it is based on ihtiyat al-wajib that is it not valid.
    
43. One who dies with Hajj already settled in his debt and he did not leave enough bequest for Hajj, qada' of Hajj on his behalf is not wajib, but if the bequest is enough for Hajj (even Hajj al-Miqati), istinabah on his behalf from the original bequest would be wajib unless he had already willed that it must be obtained from the third (thulth) in which case it should be obtained and given priority over the willing for mustahabb thing. Nevertheless, if it is not enough, the remainder should be obtained from the original bequest.
    
44. In situations in which istinabah is legitimate, direct hastening to it is wajib whether on behalf of a living or a deceased person.
    
45. It is not wajib on the living person to do istinabah from his country but it is sufficient for him to do it from the Miqat. For a deceased person on whom the obligation of Hajj is settled, it is sufficient to perform Hajj on his behalf from the Miqat, and if istinabah could not be done but from his county or another city, then it is obligatory to do it and the additional expenses should be obtained from the original bequest. However, if he had willed to perform Hajj from his country, then the will should be executed and the excess over the wage enough for Hajj al-miqati should be obtained from the third of the bequest.
    
46. If a deceased person willed Hajj al-mustahabb be performed on his behalf, its expenses would be obtained from the third.
    
47. If the heirs or the legatee become certain that Hajj had been already settled on the deceased person and they doubt about whether it had been performed or not, it is wajib to do qada' on his behalf. While if they do not know whether it had been settled or not and he had not willed it, then they are not obliged to do anything.
    
    

Conditions to be present in the na'ib

It is a condition for the na'ib to have some characteristics:
First: Adulthood (based on ihtiyat), since the Hajj of child is not valid on behalf of another to replace Hajjat al-Islam, and even the Hajj al-wajib in general.
Second: Sanity, since Hajj is not accepted from an insane person whether his sickness is permanent or comes in attacks (if he performs Hajj during the attack).
Third: Belief. The Hajj of a non-believer on behalf of someone else is invalid.
Fourth: Be acquainted with practices rules of Hajj in the way that he could perform the manasik correctly, even if he does that with a guide who teaches him each practice at its time.
Fifth: His debt if free of Hajj al-wajib for himself in this year.
Sixth: Not to be excused from some of the Hajj practices.
This condition and the rules will result from it will be cleared up in other issues when dealing with the practices of Hajj.

48. To satisfy with istinabah it is a condition to be confident that the na'ib had performed the Hajj on behalf of him who hired him. But after certainty is acquired that he had done it, it is not a condition to investigate its correctness. It is sufficient to ensure correctness in general.
    
    

Conditions to be present in that who hired the na'ib

It is a condition for the hiring person to have some characteristics:
First: Being Muslim. It is not true to perform Hajj on behalf of a non-Muslim (kafir).
Second: The hiring person should be either dead or unable to perform the Hajj by himself (i.e. if the istinabah is for his Hajj al-wajib) due to old age, sickness or extraordinary hardship and he has lost hope that he could perform it without extraordinary hardship even in the following years. While in Hajj al-mustahabb istinabah is valid on behalf of others absolutely.
And here are some issues:

49. Similarity between the na'ib and the hiring person is not a condition i.e. it is valid for a woman to represent a man, and vice versa.
    
50. It is permissible for a sarurah (person who is going to Hajj for the first time) to represent a sarurah or others whether the na'ib or the hiring person is a man or a woman.
    
51. Adulthood and sanity are not conditions for the person who hired the na'ib.
    
52. For Hajj al-niyabi to be correct it is a condition to intend the niyabah and determine the hiring person, even generally, but it is not a condition to mention his name.
    
53. It is incorrect to hire a person whose duty is to shift from completing the actions of Hajj al-tamattu` to Hajj al-ifrad, due to lack of time. However, if he hired him and accidentally his time becomes limited, he should shift and it will be valid instead of Hajj al-tamattu` and he deserves the wage.
    
54. If the hired person dies after the ihram and entrance of the Haram, he deserves a full wage, if the hiring was for the purpose of freeing the debt of the hiring person as it was clear from the generalization of hiring during the agreement process i.e. it had not been restricted by a condition that all actions be done.
    
55. If one had been hired to perform Hajj with a wage which appeared later to be insufficient to cope with his expenses, the hiring person is not obliged to complete it. And so if it exceeds, he has no right to regain the excess.
    
56. In situations where the Hajj of a na'ib is ruled to be of no substitute for that of the hiring person, then it is wajib on the na'ib to give back the wage to the hiring person if the hiring process was conditioned in that year; otherwise he must perform the Hajj, on his behalf, later.
    
57. It is not permissible to hire a person who is excused from doing some of the practices of the Hajj (the excused is that person who cannot perform the same duty of him who has the choice, a matter which leads to a defect in some of the Hajj practices). Then, if the excuse would not lead to that (as if he becomes excused only in committing some of the prohibited acts during ihram), his niyabah is correct.
    
58. If the excuse which occurs during Hajj al-niyabi would lead to a defect in the na'ib's practices, the invalidity of hiring is not remote. So, in this case it is based on ihtiyat al-wajib to reconcile about the wage and repeat the Hajj on behalf of the hiring person.
    
59. The niyabah of those who are excused from normal wuquf at Mash`ar al-Haram is invalid and if they are hired like that, they would not deserve the wage, for example: a caravan's servants who are forced to accompany weak persons or perform some of the caravan's duties and stream out from the Mash`ar to Mina after midnight. Then, if one of those mentioned should be hired for Hajj al-niyabi, he would be obliged to attend the normal (ikhtiyari) wuquf and perform the Hajj.
    
60. The Hajj of an excused na'ib is invalid no matter whether he is hired or a volunteer or whether the na'ib or the hiring person was ignorant about the excuse. And so it the case if one of them was ignorant that this excuse would be impermissible for niyabah e.g. if one was ignorant that it is invalid to satisfy the compulsory wuquf at Mash`ar al-Haram.
    
61. If the na'ib had done ihram and entered Mecca but then he became aware that he was mustati`, his ihram, then, is void and he must return back to Miqat and to ihram again for himself for `Umrat al-tamattu`, unless he had done ihram with the niyyah of the real duty, in which case his ihram is correct.
    
62. The na'ib is obliged to act according to his duty whether regarding taqlid or ijtihad.
    
63. If the na'ib has died after ihram and entering the Haram, this will be valid for the hiring person, while if he died before entering the Haram, it is invalid according to ihtiyat al-wajib. In this rule there is no difference whether the na'ib is a volunteer or is hired or whether his niyabah is for Hajjat al-Islam or other types of Hajj al-wajib.
    
64. It is based on ihtiyat al-mustahabb for a na'ib who had not performed the Hajjat al-Islam for himself, to perform `Umrah al-mufradah for himself after finishing his Hajj al-niyabi practices as long as he is in Mecca if he was able.
    
65. After finishing the practices of Hajj al-niyabi the na'ib is allowed to do tawaf for himself or on behalf of others, more over he is also allowed to perform `Umrah al-mufradah.
    
66. As the belief of the na'ib is a condition, it is also a condition for all the manasik in which niyabah is permissible, like tawaf, ramy and hady.
    
67. Based on ihtiyat, it is wajib on the na'ib to do, by himself, the practices for which he had accepted to do niyabah.