Tirmidhi maintained contacts with other contemporary mystics in his region. From sections  and  ff. it is obvious that he was especially interested in the case of Yahya b. Mu-adh al-Razi. Moreover letters from Tirmidhi survive. For the text and translation of his letter to Abu CUthman al-Hiri (d. 298/910) in Naysabiir see respectively Iewiib 190-92, 19th mas'ala, and l:IT 117-19; and for a partial translation of his letters to Muhammad b. al-Fadl al-Balkhi in Balkh (d. 320/932 in Samarqand) see l:IT 119-126. The principal theme discussed in this correspondence is sidq. one of the important subjects dealt with in the Sira, but the question of Friendship with God is not mentioned. There is, however, evidence that in Balkh, an important city in the vicinity of Tirmidh, there were mystics (see TM 551; van Ess, Theologie II, 544 ff.) who discussed and reflected on the nature of Friendship with God, and in a quite different manner from Tirmidhi. The following saying is attributed to Abu Bakr Muhammad b. Hamid
al-Tirmidhi who was close to the spiritual masters of Balkh: al-wali fi satr hiilihi abadan (The Friend always conceals his state) (Tir. Min. 265). This contradicts one of the principal tenets of the Sira (; ). In any case what survives in the way of such speculation is scanty indeed. Generally speaking, it is striking how small a role discussion of Friendship with God plays in the handbooks on classical Sufism. Hujwiri/Jullabi is an exception in this respect (see Introduction 5). Abu Nasr al-Sarraj treats the subject in the Gbeltuiit (Gramlich, Schlaglichter 587 f., sub 146), but the anonymous Adab el-muliik is silent in this regard. Qushayri is the first author to devote an entire chapter to Friendship with God in his famous Risiila (Gramlich, Sendschreiben 358 ff., sub 38) which in several of its formulations appears to be dependent on the Sira without acknowledging it.