The testimonies provided by human beings before (prophecy), during and after Jesus's life. The sermon deals with the first case.

Introduction Echoing the prophet (thema), the issue is why God allows a people so evil and unfaithful like the Turks to prosper and oppress the Christians: “Ex quo gentem infidelem, impiam et prevaricatricem thurcorum permittit prosperari et christianum populum opprimere?” (f. r5r). Several quotations from Job and Jeremiah. The duration of this oppression surprises the people, who don’t understand its causes; it causes also grumbling about God’s injustice. “Quare licet thurci impii conculcaverunt tuos fideles, devorant, lacerant, et tandiu affligunt? Sunt iam fere anni 870 ab initio secte usque nunc, nec tamen apparet signum consumationis ipsius, de quo nedum multi mirantur tante durationis causam non invenientes, verumetiam plerique murmurant de dei providentia et quissima iusticia” (f. r5r). It's not clear to what the 870 years exactely refer (if it is the Egira, it would refer to 1492 (it would be puzzling); yet later in the sermon, the origin of the Turks is indicated as 666, so it cannot be a reference to it).    Divisio (see above) 

1. Persecution is just since it is a punishment: “Ista christianorum atrox persecutio mahumetica iuste nobis est inflicta propter nostram punitiuonem, quod probemus tripliciter” (f. r5r); the evidences are: a) prophecies, b) reasons, c) revelations. 1.1. Prophecies. In the Bible the prophets announced the persecution of the synagogue – ad fortiori, there are prophecies of the persecutions of the Church. The first and key reference (here and below) is the Pseudo-Methodius. There is first a long series of quotations, which contain vivid and dramatic description of the Muslim violence on Christians. The quotations already contain two key concepts: this is a punishment (castigatio) for the way Christians sinned against the divine law; the persecution will reveal the true faithful (fideles). Attention to geographic description, a sort of geopolitics of history (as in other sermons); see f. r5v.  The cause was a triple separation: from Christ, heresy; from the apostolic seat, disobedience; from Roman empire, rebellion (the reference here is to the Greeks). Interesting reference to the discourse of the Venice orator, Bernardo Giustiniani in front of the pope, as a way to chart (again) the Turkish expansion (in which, stand out the lost of two empires, those of Constantinople  and Trebizond). Cyril’s letter [?], interpreted by Joachim of Fiore’s commentary to the Lamentations: the buck that eats the flash of the sheep symbolizes Muhammad that eats alive the Christians (the flash of Christ, the sheep) who join his sect (secta): “et dentibus suis carnis crudas agnorum dilacerabit, quia parvuli et adulti utriusque sexus relicta fide Chirsti sectam Mahumeti assument” (f. r6r). Reference also to the prophecies of Hildegard of Bingen (with the date 1143) and of Birgitta of Sweden. 1.2. Reasons: justice and sins. With a pessimistic note: while at the time of the martyrs the persecution strengthened the faith, now it decreases it: “In presenti autem afflictione fides non tantum augmentatur, quantum diminuitur, ac maxima blasphemia deo et sanctis eius infertur” (f. b6v). The persecution is due to the crimes of the Christians, mainly three major sins (crimina): “Unde causam huiuscemodi persecutionis ex scripturis inveniemus tria horrenda crimina in ecclesia dei multiplicata sunt”: sodomy (peccatum contra naturam), with references to Letter to Romans and to previous castigations of sodomites: the deluge, the destruction of Sodom, and their death during Christmas night (source Jerome: “et ut dicit Hieronimus: in nocte nativitatis, anteque Christus nasceretur, in hoc peccato laborantes sunt extincti”; f. r7r); ignoble taking of the holy communion, which is labeled as “crimen maximum”, with reference to Thomas Aquinas, since it is “as if one kills Christ”; disobedience, in particular applied to schismatics. 1.3. Sure revelations. Interpretation of Apocalypse 16, the seven bowels (phialae) full of the wrath of God, which represents seven persecutions to the Church. The fifth are the Turks, since the throne of the beast is Constantinople – with a reference to “quodam tractatu disputato in capitulo generali fratrum predicatorum” (f. r7r). The sermon mentions also the vision of a Carthusian in the convent of Raromot (!) in Carniola: in an ecstasy he was brought in front of tribunal of Christ, who asks him why the Church prays so much while instead it has abandoned him. At the announcement of the tribulations that will soon hit the Church, the monk asks two things, which remains without reply: whether also Rome will be conquered by the Turks, and if the faithful will succumb in the spiritual battle: “Demum post modicum resumptis viribus frater de duobus petiit informari a Christo, scilicet: An Rhomana civitas esset a Thurcis capienda; et an in futuro bello, quod in spiritu cognoverat committendum, ipsi fideles succumberentur. Ad que respondit Christus quod non expediret hoc ipsum scire” (f. r7v) Invective against vices, as a way to mention again the main sins.
2. The end of the Turks’ persecution is close [yet, not so close after all] and the sermon deals with two aspects: why it was so long; when it will end. 2.1. The domination was so long due to two reasons: first, as the Postilla of Peter of Burgos points out, they are not idolaters as previous persecutors, so God is less pressured to intervene. It started in the year 666 (symbolism of Revelations), yet “in ista secta mahumetica pessima est infidelitas sine idolatria”; second, they do not directly only to apostate the faith: “nec directe cogunt ad apostatandum a fide” – they just ask to pay a fee, and to pay it does not diminish the dignity of the Church: “Unde vivere abicere et sub iugo servitutis non minuit veritatem ecclesiastice dignitatis” (f. r8r) [a sort of realistic position]; third, they do not recognice the divinity of Christ, yet they appreciate his human qualities – so again God is less compelled to intervene.
   2.2. When will it end? Ample quotation of the Pseudo-Methodius, from which it is derived the number of 56 years, yet without being sure where their start has to be put: “Nescimus tamen unde debent incipi, si a captione Costantinopolitane vel a dominio perfecto grecie” – counting from the fall of Constantinople it would be until 1509, yet it is mentioned – as other possible starting point – the Turkish conquest of Albania (i.e. 1478). Reference to an Islamic prophecy of their own defeat, mentioned by Scotus saying that it was found in a Muslim book in Damietta, which prophesizes that a Christian king will conquer and destroy Mecca and disperse the bons of Muhammad - this will fulfil the promise of the announced of the Gospel in all the word (Matthew 28) and will be end history [cfr. link with the prophecy of the last emperor]. The sermon mentions also the revelations of Hildegard of Bingen, Brigitta of Sweden  and Catherine of Siena who praised preaching to convert the people. Further reference is to Nicholas of Lyra, who refers to the Liber Iudicum ordinariorum a Jewish book of prophesy, connected with the announcement of the raising son of the widow of Zarephath, which states that the world will last 6000 years: 2000 under vanity, 2000 under law, 2000 under the Messiah. Since the period under the Messiah is of 2000 years, and during it the Gospel will be announced to everyone, the end of the Muslim domination should be close [yet, it remains quite an ample margin!]. How it will happen? Again a reference to Pseudo-Methodius: when all seems lost, it will rise “rex christianorum et romanorum”... 3.  There are two reasons why their domination cannot last [sic!]: Muslim usurped the power, conquering it only by means of their weapons; their origin is mean – this is true for Muhammad but even more for the Turks - here there is a long insertion on their history, taken from the Chronicon by Antoninus of Florence – remote link with the history of Troy, their entrance in Persia as people of herders, gradual affirmation, arriving until the conquest of Constantinople in 1453 under Muhammed II.
   Final invocation to God, asking his intervention soon – with a last mention of the prophecy of Pseudo-Methodius about the role of the king of Huns, i.e. now Hungary.