Sad Meydan is one of the oldest mystical works in the Persian language, which was the result of Khajeh Abdollah Ansari's sermons in Muharram 448 AH. The twenty-first field (Meydan) of Sad Meydan is about ‘tavakkol’ (trust) and it is stated in it: “Trust is ghantare-ye yaghin (the bridge of certainty) and emad-e iman (the pillar of faith) and mahall-e ekhlas (the place of sincerity)”. This statement is also mentioned in other books such as Tafsir Kashf al-Asrar, Ons al-Taebin and Hadighat al-Haghighat. However, in the manuscripts and prints of these texts, the combination of ‘mahall-e ekhlas’ (The place of sincerity) is also found in four other forms: mahakk-e ekhlas (the touchstone of sincerity), mokh-e ekhlas (the brain of sincerity), mikh-e ekhlas (the peg of sincerity), mahz-e ekhlas (the absolute of sincerity). Each of the editors of these texts has accepted and printed this combination in some way.
Introduction
The Sad Meydan by Khajeh Abdollah Ansari (396-481 AH) is one of the oldest mystical works in Persian and is actually the first independent work in Persian in describing the stages of the austerity, consisting of one hundred ‘Meydan’ )fields( that begin with ‘tawba’ (repentance) and ends with ‘fana’ (destruction) and ‘bagha’ (survival). This work is not authored by Khajeh Abdollah, but it is the written form of Khajeh's words in his sermons in Muharram 448 AH, which were written down by his anonymous disciples. There are few manuscripts left from the Sad Meydan, the oldest of which dates back to 852 AH, which is 371 years away from the time of the author's death.
The twenty-first field of Sad Meydan is about ‘tavakkol’ (trust) and it is stated in it: “Trust is ghantare-ye yaghin (the bridge of certainty) and emad-e iman (the pillar of faith) and mahall-e ekhlas (the place of sincerity)”. This statement is also mentioned in other books such as Tafsir Kashf al-Asrar, Ons al-Taebin, and Hadighat al-Haghighat. However, in the manuscripts and prints of these texts, the combination of mahall-e ekhlas (The place of sincerity) is also found in four other forms: mahakk-e ekhlas (the touchstone of sincerity), mokh-e ekhlas (the brain of sincerity), mikh-e ekhlas (the peg of sincerity), and mahz-e ekhlas (the absolute of sincerity). In this research, we have examined this expression from Sad Meydan in its two original editions and by finding variants of it in other texts composed to show the superior variant and the correct form of the expression.
 Review of the Literature
First time in 1934 Edgar Blochet in the Catalogue des manuscrits persans de la Bibliothèque nationale (tome quatrieme N^os 2018-2481) introduced a manuscript of Sad Meydan dated at the beginning of the 17th century AD.
 A year later, in 1935, Hellmut Ritter in the Der Islam, in an article entitled 'Philologika', identified another manuscript of it is preserved in the library of Shahid Ali Pasha in Turkey dated 1499 AD.
After that in 1954, Serge de Beaurecueil edited Sad Meydan based on these two manuscripts. Then, Habibi in 1962 and Ravanfarhadi in 1976 in Afghanistan and Ansari in 1984 in Iran published the same text edited by Beaurecueil with minor changes.
Then, two new manuscripts were identified from Sad Meydan: the version of Morad Molla's library in Turkey dated 1448 AD and the version of Bombay dated 16th century AD. At this time, due to the fact that the writing date of one of these new versions (i.e. Morad Molla's version) was older than all the other versions, it became necessary to re-edit it. To this end, Molaei published Sad Meydan in the book Majmu`e Rasael-e Farsi-ye Khajeh Abdollah Ansari (The Persian Collection of Khajeh Abdollah Ansari) in 2010.
 Methodology
This research was conducted using a descriptive-analytical method and by identifying various sources in which this phrase is mentioned. The author tries to show the correct variant by referring to several reasons of codicology, language, and rhetoric.
 Results
Among the variants, mahall-e ekhlas is the best variant for the following reasons:

A) The credibility and greater value of Kashf al-Asrar Kashf al-Asrar has been edited based on the Yeni Jame version written between 716-703 AH and the Topkapi Sarayi version written before 700 AH, but the writing date of the other versions is later: the oldest version of Sad Meydan is dated 852 AH. The original version of Ons al-Taebin is probably from the end of the 11th century or the beginning of the 12th century of the Hijri or years before that and the oldest version of Hadighat al-Haghighat is dated 706 AH. In addition, due to the repeated variant of mahall-e ekhlas in two different places of Kashf al-Asrar, the probability of its authenticity is very high.
B) The combination of mahall-e ekhlas is found in the texts that were written before Khajeh Abdollah or at the same time as him, such as Abu Abd al-Rahman Solami (died 412 AH) in the book Ketab-e Fosul fi al-Tasavvof and also Abu al-Qasim Al-Qoshayri in Resale- ye Qoshayriye (authored 438 AH).
C) The use of an additional compound in which the first word is the word mahall (place) is more or less seen in the works of Khajeh Abdollah. Moreover, the use of this type of compound is also abundant in the ancient Sufi texts, which were written before Sad Meydan, such as the Sharh al-Ta`arrof le-Mazhab-e Tasavvof by Abu Ibrahim Ismail Mostamli Bukhari (died 434 AH). It is also found in the texts that were written during the lifetime of Khajeh Abdollah, such as Kashf al-Mahjub by Ali bin Osman Hojviri (died 465 AH).
D) The variant of Moulaei is mahakk-e ekhlas. It should be said that the conversion of mahall to mahakk is quite possible because in ancient times the letter ‘ک’ (K) was written quite similar to "ل" (L). Therefore, some scribes have written mahakk and mahall as the same. Therefore, among the manuscripts of Persian and Arabic texts, sometimes mahakk is substituted for mahall.
E) Sheikh Jam said that the faith of every believer is pierced in three areas: mokh-e ekhlas (the brain of sincerity), emad-e iman (the pillar of faith), and pol-e yaghin (the bridge of certainty). It is clear that ‘pillar’ and ‘bridge’ are places where the presence of holes is possible, but it is impossible to have a hole in ‘mokh’ (the brain) and ‘mix (the peg), a hole through which a thief passes and steals goods. In fact, it is mahall-e ekhlas that can be pierced, a hole through which a thief can pass and steal goods.
F) But mahz-e ekhlas (the absolute of sincerity) which is the variant of the Calcutta manuscript of Ons al-Taebin, is certainly an oversight and mistake, because, on the one hand, it comes in only one version, and on the other hand, this variant does not fit with other parts of Khajeh Abdollah's sentence. Because each of the statements "trust is the bridge of certainty" and "trust is the pillar of faith" and "trust is the place of sincerity" rhetorically includes simile, but the statement "trust is the absolute of sincerity" is completely different.

It is useful and effective to use Sad Meydan as a secondary and auxiliary source in editing other books such as Kashf al-Asrar, Ons al-Taebin, and Hadighat al-Haghighat. Knowing the secondary sources (including possible sources of the author) and referring to them is very effective in solving the problems related to the editing of texts from which ancient and authentic manuscripts are not available, as well as in explaining the words and their problems.