When the wayfarer to Allah has announced, by his takbirs, that Allah is greater than any description, and by testifying to His Divinity exclusively confined all attributes and praise, or, actually, every influence and effect, to Allah, and confessed his incapability of managing the amr, and by the testimony to Messengership and Guardianship, he has chosen his comrade and company and adhered to the sacred position of successorship and guardianship -as it is said: "The companion (first) then the journey"  then, with quite an explicit tone, he is to prepare his visible and invisible powers for the Salat, announcing the presence to them by saying: "Hayya 'alas-Salat", (come to the Salat) twice . Its repetition is intended to complete awakening [tanbih] and waking up [iqaz], or one is for the inner powers of the kingdom, and the other is for the outer powers of the kingdom, since they also accompany the salik on his journey, as has already been said, and will follow, too.
In this stage, the discipline of the salik is to tell his heart and powers, even the innermost of the heart, that the time of presence is near so as to prepare himself for that, fully observing the formal and the spiritual disciplines. Then he is to announce the general secret and result of the salat, by the calling: "Hayya 'alal-falah" and "Hayya 'ala khayril 'amal (come to the best of deeds) so as to wake up the fitrat (disposition = nature), because prosperity and salvation are absolute happiness, and all the human beings love absolute happiness by nature. The innate nature [fitrat] is in quest of perfection and comfort. The truth of happiness is the absolute perfection and absolute comfort, and that is brought about in the salat, which is the best of deeds, cordially, formally, outwardly and inwardly. This is because the salat, according to its form and appearance, is a great and comprehensive remembrance and a praise of the Greatest Name, which encompasses all the divine affairs [shu'un]. For this reason, the adhan and the iqamah open with the word "Allah" and end with it, and Allahu akbar (Allah is Greater) is repeated in all stages of the salat, and the three tauhids (professions of the Unity of Allah), which are the delight of eyes of the holy men, are effected in the salat, in which the form [surat] of absolute annihilation and complete return are mixed. According to the interior and the truth, it is ascension to the proximity of Allah, the truth of reaching the Beauty of the Absolute Beautiful and vanishing in that Sanctified Essence, dearly loved by the inborn nature [fitrat]. It is by the salat that the complete calmness, absolute comfort and the complete mental happiness are achieved: "Surely by Allah's remembrance are the hearts set at rest." 
Therefore, the absolute perfection, which is attaining to Allah's Court, joining the Necessary Limitless Sea, discerning the Eternal Beauty, and being immersed in the Sea of Absolute Light, is effected in the salat, in which absolute comfort, complete rest and perfect calmness also appear, bringing about the two corners of happiness. So, the salat is perfect prosperity, and it is the best of the deeds. The salik will have to repeat this divine grace, to remind the heart and to wake up his disposition [fitrat] , and after having it in his heart, his inner nature would attach importance to it and observe it, since it looks for perfection and happiness. The same point is true in respect of the repetition. When the salik reaches this stage, he announces his presence by saying: "qad qamatis-salat" (The salat has just started). Then, he is to see himself at the Presence of the Master of the kings of the worlds of existence and the Sultan of the sultans and the Absolute Great, and to inform his heart about the dangers of the Presence, all of which are due to the incapability and the inefficiency of "the possible", and to feel ashamed of not carrying out the any, approaching, with the steps of fear and hope, towards the Generous. He is not to regard himself possessing travelling provisions and company. He is to see his heart empty of safety, not to think his deeds good ones; rather, worth not a penny. Should this state become firm in his heart, he would hope to get Allah's care: Nor Who answers the distressed one, when he calls unto Him, and removes the evil?' 
Connection and Completion
Muhammad ibn Ya'qub, quoting Abu 'Abdullah as-Sadiq (AS), says: "When you recite the adhan and the iqamah, two rows of angels will perform the Salat behind you, but if you said the iqamah (only), one row of the angels would perform the Salat behind you.',  There are many other hadiths to the same effect, some of which say that the length of each row is as the distance between the east and the west.  Another hadith says that when Imam as-Sadiq (AS) was asked about the length of each row, he said: "The length of the shortest row is as the distance between the east and the west, and the length of the longest is as the distance between the heaven and the earth."  In some narratives it is said that if he said the iqamah without the adhan, an angel would stand at his right side and another at his left side,  and other similar narratives. The difference among the narratives may be due to the difference among the knowledge and the sincerity of the musallin, as can be inferred from some narratives in this respect, such as the narrative concerning performing the salat with the adhan and the iqamah in the desert or wasteland.  In short, when the salik sees himself leader of the salat for the angels of Allah, and his heart as the leader of his visible and invisible powers, and gathers, with the adhan and the iqamah, his visible and invisible powers, together with the angels of Allah, he is to regard his heart -which is the best of the external and internal powers, and the intercessor for the other powers - as to be an Imam. And, as the heart is liable for the recitings of the ma'mumin [musallin] after its leadership, and as their faults are undertaken by it, the salik is to be quite keen and a good observant of its presence, and to completely guard the disciplines of the Sacred Presence, making the most of this Sanctified Meeting, admitting the great importance of the attention and the support of the angels of Allah, taking them to be of the favours of the Real Benefactor, and acknowledging his incapability of giving the due thanks to His Sacred Majesty for these great blessings. Surely He is the Benefactor!
. Wasai'lush Shi'ah, vol. 8, p. 299. "Book of Hajj", chs. on "The Manners of Travel", ch. 30, hadith 11, quoted from al-Barqi's Mahasin, p. 357. Similar concepts are in some other narratives, such as: "Inquire about the company before the journey" as in Nahjul Balaghah, ed. by Faydul Islam, p. 936, and "The company (first), then the journey", in al-Ash'athiyat, p. 164, ch. on "Bad Neighbouring".
. Surah ar-Ra'd: 28.
. Surah al-Naml: 62.
. Furu'ul Kafi, vol. 3, p. 303, "Book of The salat" ch. on "Starting the Adhan and the Iqamah", hadith 8.
. Thawabul A'mal, p. 54, "The reward of the one who performs the salat with the Adhan and the Iqamah", hadith 2.
. Wasa'ilush-Shi'ah, vol. 4, p. 620, "Book of the salat" , chs. on "The Adhan and the Iqamah", ch. 4, hadith 4.
. Ibid., Hadith 9: " O Abu Dharr, your Lord boasts over His angels for three persons: a man in a waste land ..."