There is no contagion, fleeing from the leper, and prohibition of evil omens

It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "The contagion of disease (by itself) and taking bad omens have no reality. (If disease spreads merely by passing from one to another, then) who gave the disease to the first one?"
Imam Ibn Abi Shaybah recorded this hadith in his al-Musannaf, and its narrators are thiqat (trustworthy).

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) passed near the place called Usfan, and there was a leper (a person with leprosy) there. He (peace and blessings be upon him) (on seeing him) quickened his pace and said: "If anything among diseases can be contagious (passing from one to another), it is this (leprosy)."
Imam al-Harith bin Abi Usamah recorded it in his Musnad. In its chain is a narrator named al-Khalil bin Zakariyya, who is da'if (weak); however, other authentic hadith about keeping away from leprosy and taking precautions exist in the books of the Sahih collections.

It is narrated from Ata (may Allah have mercy on him) that the Messenger of Allah (peace and blessings be upon him) said: "No disease passes from one to another by itself, there is no basis for bad omens, there is no ill luck in Safar (the month), and the hamah (taking an evil omen from the owl) has no standing." Ibn Jurayj says: I asked (Ata): "From whom are you transmitting this narration?" He replied: "It is a mustafid (widely known and famous) hadith." I asked: "What is meant by Safar?" He said: "People say it is a pain of the stomach that afflicts a person."
This narration is sahih (authentic), and its basic contents are also narrated in Sahih al-Bukhari and Sahih Muslim.

It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Disease flying across and infecting (by itself, without Allah's command) has no reality, nor is there any basis for the hamah (that is, the ignorant belief of taking an evil omen from the owl or of the soul becoming a bird), nor can a sick person make a healthy person ill (merely by his own natural power)."
Imam Abu Ya'la narrated it through Uthman bin Abi Shaybah and Ibn Numayr, while its second chain was transmitted by Abd al-A'la bin Hammad through Hammad bin Shu'ayb from Habib bin Abi Thabit, who heard from Tha'labah that he heard Sayyiduna Ali (may Allah be pleased with him) say this.

It is narrated from Abu Talhah al-Khawlani (may Allah have mercy on him) that Sayyiduna Umayr bin Sa'd (may Allah be pleased with him), who because of his matchless qualities was called "Nasij Wahdihi" (unique of his age), was with a few people of the land of Palestine. We were sitting on a large platform in his house when he said to his servant: O boy! Water the animals. In the house there was a large stone trough, and the servant brought them to be watered. He asked: Where is such-and-such a she-camel? The servant submitted: She has mange, and blood (or water; the narrator Ibrahim is in doubt) is dripping from her body. He ordered: Bring her too to be watered. A man present in the gathering said: (If she is put with the other camels) then all the camels will get mange this way. He said: Water her, for I heard the Messenger of Allah (peace and blessings be upon him) say: "Disease (flying across and) infecting (by itself) has no reality, nor is taking bad omens permissible, nor does the hamah (the owl, or some superstition of the Time of Ignorance) have any standing. Have you not seen the camel that is (perfectly healthy) in the desert, and then suddenly a mark appears on the raised flesh of its chest (kirkiratihi) or the soft parts of its belly (maraqqihi) which was not there before? So (tell me), who made the first camel ill?"
Musnad Abi Ya'la: 2492. Its chain is hasan (good); al-Hafiz al-Haythami declared its narrators in Majma' al-Zawa'id to be narrators of the Sahih.

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he said: "A bad omen or evil augury does not harm anyone at all (in itself), except the person who lets it take hold of himself and starts taking bad omens from it."
Imam Ibn Abi Shaybah recorded this athar in al-Musannaf (26038), and its chain is sahih (authentic).

It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "A bad omen is only that which turns you back (from some undertaking) or urges you to press ahead (relying on it)."
Imam Abu Ya'la recorded it. In its chain is a narrator named Ja'far bin al-Zubayr, who is da'if (weak); however, in its meaning it is supported by other authentic hadith.

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "He is not of us (of the way of the Muslims) who practises magic or has magic done for him, nor the one who takes a bad omen or has a bad omen taken for him, nor the one who adopts soothsaying (the trade of telling of the unseen) or has soothsaying done for him."
Imam al-Bazzar (may Allah have mercy on him) says that Abu Musa narrated this hadith to us through Abu Amir, and he further said: We know of this hadith only through this chain and this route.

It is narrated from Umm Alqamah (the freed slave-woman of Sayyidah Aishah (may Allah be pleased with her)) that she brought a little boy to Sayyidah Aishah (may Allah be pleased with her) so that she would supplicate for him (for good and blessing). Meanwhile, when the people lifted the pillow on which the child was lying, Sayyidah Aishah (may Allah be pleased with her) saw a razor placed under it. She (may Allah be pleased with her) asked: "What is this?" The people answered: (We have placed it here because) we consider it a means of protection from the evil of the jinn and from the child's sudden fright or alarm. The narrator relates that Sayyidah Aishah (may Allah be pleased with her) took it and threw it away, and said: "Indeed the Messenger of Allah (peace and blessings be upon him) intensely hated bad omens, superstition and evil augury, and disliked them."
Imam Abu Ya'la recorded it in Musnad Abi Ya'la. Its chain contains the narrator Abd al-Rahman bin Abi al-Zinad, whose memory has been criticised; however, the prohibition of bad omens and superstition is established by authentic hadith.