allah, the exalted, says:

"invite (mankind, o muhammad (pbuh)) to the way of your rubb (i.e., islam) with wisdom (i.e., with the divine revelation and the qur'an) and fair preaching.'' (16:125)

699. shaqiq bin salamah reported: ibn mas`ud (may allah be pleased with him) used to preach to us once every thursday. a man said to him: "o abu `abdur-rahman, we love your talk and we wish that you preach us every day.'' he said: "there is nothing to prevent me from doing so, but i don't lest i bore you. i follow the same method in preaching to you that messenger of allah (pbuh) adopted in preaching to us for fear of boredom.''
[al-bukhari and muslim].

commentary:  this hadith throws light on the indispensability of equilibrium in sermons and discourses so that people may not shun them. monotony, though well designed, is repugnant to human nature. similarly, teaching and instructional training requires such hours which may facilitate people's willing participation. compulsion and economic incentives rarely work in spiritual spheres. we are also informed of the companions' keenness to follow messenger of allah (pbuh).

700. `ammar bin yasir (may allah be pleased with them) reported: i heard messenger of allah (pbuh) saying, "prolonging salat (prayer) and shortening the khutbah (religious talk) indicate the religious knowledge of the person. make your salat long and your sermon short.''
[muslim].

commentary: a prolonged salat (prayer) by no means implies a disregard of worshipper's constraints. it is indeed forbidden. rather the imam is emphatically told to perform a brief and concise salat because his followers also include, amongst others, the weak, the aged and the sick people. herein an emphasis is laid on prolonging salat instead of khutbah (religious talk). the friday khutbah is meant to be brief. it must not be too lengthy in relation to a brief salat offered heedlessly and in sheer haste. salat must be offered in all humility and with full attention and concentration of mind. furthermore, a worshippper ought to maintain a well-paused equilibrium in different postures of its performance. brevity should be kept in view of khutbah.

701. mu`awiyah bin al-hakam as-sulami (may allah be pleased with him) reported: while i was in salat with messenger of allah (pbuh), a man in the congregation sneezed and i responded with: `yarhamuk-allah (allah have mercy on you).' the people stared at me with disapproving looks. so i said: "may my mother lose me. why are you staring at me?'' thereupon, they began to strike their thighs with their hands. when i saw them urging to me to remain silent, i became angry but restrained myself. when messenger of allah (pbuh) concluded his salat. i have never before seen an instructor who gave better instruction than he, may my father and mother be sacrificed for him. he neither remonstrated me, nor beat me, nor abused me. he simply said,"it is not permissible to talk during salat because it consists of glorifying allah, declaring his greatness as well as recitation of the qur'an,'' or he said words to that effect.'' i said: "o allah's messenger, i have but recently accepted islam,  and allah has favoured us with islam. there are still some people among us who go to consult soothsayers.'' he said, "do not consult them.'' then i said: "there are some of us who are guided by omens.'' he said, "these things which come to their minds. they should not be influenced by them.''
(muslim).

commentary:  this hadith emphasizes four points. firstly, as no talk is allowed in salat (prayer), nobody can utter benedictory words for a sneezer either. secondly, this hadith throws light on the prophet's way of imparting moral instruction to others. he would prudently enlighten ignorant people on islam, avoiding to express his resentment over their lapses which simply betrayed their lack of knowledge. this has a lesson for `ulama' and preachers. thirdly, muslims are prohibited from consulting soothsayers. fourthly, belief in bad omens is also prohibited. divinations and presages were the popular fallacies of arabs in the pre-islamic epoch. islam abolished them. yet, once again these absurdities have caught the fancy of ignorant muslims. may allah guide them!

702. `irbad bin sariyah (may allah be pleased with him) reported: one day, messenger of allah (pbuh) delivered a very effective speech, as a result, eyes shed tears and hearts became softened. a man said: "o prophet of allah! it sounds as if this is a farewell speech, so advise us.'' he (pbuh) said, "i admonish you to fear allah, and to listen and obey even if a black slave has been appointed as your leader. for whoever among you lives after me will see much discord. so hold fast to my sunnah and the sunnah of the rightly-guided caliphs who will come after me. adhere to them and hold fast to them. beware of bid`ah (in religion) because every bid`ah is a misguidance.''
[abu da wud and at-tirmidhi].

commentary: according to this hadith, the best sermon may be defined as brief, comprehensive, appealing and beneficial. refer to the commentary on hadith no. 185.