After the ideas of Islam were introduced to the Arab society by Muhammad, a complex system of values emerged, combining the spirit of manliness (murūwah) and kinship solidarity (ʿaṣabiyyah) which reigned among the Arabs from times immemorial, with a new religious consciousness (dīn). Scholars who have been examining the ethical system which appeared in the 7th century Arabia (Farès, Lecomte, Rezvan, Bravmann) found that, generally, Islam did not oppose pre-Islamic moral values, but rather approved and even reinforced them. A significant point mostly overlooked in this discussion is that when poetry is concerned, a certain conflict between pre-Islamic morality and the norms of Islam was inevitable. The goal of the paper is to argue this thesis examining the problem of slander as one of the most salient points of tension between Arab poets and religious ethics in the first centuries of Islam. Placing the question into the ethical paradigm of murūwah, ʿaṣabiyyah and dīn, I reconstruct the historical and exegetical discussion to trace the origins of the problem and to gain new insights into the social conditions of the state founded by Muhammad. For this, I use the diwāns of 7-8th century poets' (Aʿšā, Ḥuṭayʾa, Ḥassān ibn Ṯābit, Jarīr, Aḫṭal and some others), their biographies provided by Ibn Qutayba, Iṣfahānī and Balāḏurī, historical and literary works by Jāḥiẓ, Ibn Ḫallikān, Ibn Rašīq and Ḥuṣrī, and the collections of hadīṯ reports by Buḫārī, Ibn Kaṯīr, Hayṯamī and Aṣbahānī. The mentioned method and data allow me to come to the following conclusions. After the advent of Islam, poets' behavior was exposed to the criticism of a religious establishment who sought to maintain a certain social order protecting the young Ummah from moral degradation and inner instability. Accordingly, the ethics of a good poet was defined by his abidance by the norms of Islam in interacting with all the members of the Ummah. At the same time, poets have maintained the pre-Islamic ways of expression developed for ideological tribal wars in which any means were applied to make verses effective, and only one's commitment to his tribe was defining the ethics of actions. In these circumstances, a conflict was inevitable, because in the 7th century, composing satires became a well-paid profession outside the tribal world and many outstanding poets left their tribes in search of earning opportunities.