Praise be to Allaah.
With regard to the first question:
The answer is in two parts. Firstly, the belief mentioned in the question is not correct; it is a kind of innovation and misguidance which has no basis in sharee’ah, and is not indicated by the Qur’aan or Sunnah.
Secondly, this belief goes against the sharee’ah of Islam in several ways:
(i)The belief that someone will die during this period. It is not permissible to believe this because death and life are in the hand of Allaah and the appointed time of man’s death is something of which Allaah has kept the knowledge to Himself. No one among mankind knows when he will die. This is something which Allaah has not told to any of His creation. Hence the Prophet (peace and blessings of Allaah be upon him) said, in the hadeeth whose authenticity is agreed upon which was narrated from Abu Hurayrah (may Allaah be pleased with him), in the lengthy hadeeth of Jibreel: “There are five things which no one knows except Allaah.” Then he recited the verse (interpretation of the meaning):
“Verily, Allaah, with Him (Alone) is the knowledge of the Hour, He sends down the rain, and knows that which is in the wombs. No person knows what he will earn tomorrow, and no person knows in what land he will die. Verily, Allaah is All-Knower, All-Aware (of things”
(Narrated by al-Bukhaari, 48; Muslim, 10)
Claiming that marrying during this period will lead to death is a claim to have knowledge of the unseen, and everyone who claims to have knowledge of the unseen is lying. Hence the leaders of falsehood are those who claim to have some knowledge of the unseen.
(ii)This also undermines faith, because it implies a lack of belief in the Divine will and decree (al-qadaa’ wa’l-qadar). Hence the Prophet (peace and blessings of Allaah be upon him) taught Ibn ‘Abbaas, when he was a boy, “Know that if the nation were to gather together to benefit you in any way, they would not be able to benefit you in any way except that which Allaah had decreed for you, and if they were to gather together to do you harm in any way, they would not be able to harm you except that which Allaah had decreed for you. The pens have been lifted and the pages have dried.” (Narrated by al-Tirmidhi, Sifat al-Qiyaamah, 2440; classed as saheeh by al-Albaani in Saheeh Sunan al-Tirmidhi, no. 2043). It was narrated that ‘Abd-Allaah ibn ‘Amr ibn al-‘Aas said: “I heard the Messenger of Allaah (peace and blessings of Allaah be upon him) say, ‘Allaah decreed the fate of His creatures fifty thousand years before He created the heavens and the earth.’” (Narrated by Muslim, al-Qadar, 4797)
(iii)It also undermines Tawheed and its perfection, because it involves regarding something as an evil omen and pessimism. It says in the hadeeth narrated from Abu Hurayrah (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: “There is no ‘adwaa [contagion, transmission of infectious disease without the permission of Allaah], no tiyarah [superstitious belief in bird omens], no haamah [refers to a Jaahili Arab tradition described variously as: a worm which infests the grave of a murder victim until he is avenged; an owl; or the bones of a dead person turned into a bird that could fly], and no Safar [the month of Safar was regarded as “unlucky” during the Jaahiliyyah].”
(Narrated by al-Bukhaari, al-Tibb, 5316)
Tatayyur (superstitious belief in bad omens) means pessimism. It was narrated in the hadeeth of Ibn Mas’ood that the Prophet (peace and blessings of Allaah be upon him) said: “Tiyarah (believing in evil omens) is a kind of shirk.”
(Narrated by al-Tirmidhi, al-Siyar, 1539; classed as saheeh by al-Albaani in Saheeh al-Tirmidhi, no. 1314)
It should be noted that superstitious belief in bad omens contradicts Tawheed in two ways:
Firstly, superstitious belief prevents one from putting one’s trust in Allaah and makes one depend on someone other than Him.
Secondly, it causes people to depend on things that have no basis in reality, for there is no connection between getting married in this month and whatever may happen subsequently. Undoubtedly this undermines Tawheed, because Tawheed means worship and seeking help. Allaah says (interpretation of the meaning):
“You (Alone) we worship, and You (Alone) we ask for help (for each and everything).”[al-Faatihah 1:5]
“So worship Him (O Muhammad) and put your trust in Him”
Hence ‘Aa’ishah (may Allaah be pleased with her) used to say that the Prophet (peace and blessings of Allaah be upon him) married her in Shawwaal and consummated the marriage with her in Shawwaal and she was the dearest and most beloved of his wives to him. The Arabs used to regard this month as inauspicious and they used to say that if a person got married in Shawwaal, the marriage would not succeed, but this is not true.
In the case of one who believes in evil omens, one of two things must apply:
Either he will give up, respond to the “bad omen”, and not take action, which is the worst kind of superstition and pessimism, or he will go ahead, but he will be anxious and worried, fearing that he will be affected by this bad omen. This is less serious, but both detract from Tawheed and adversely affect people. (See al-Qawl al-Mufeed by Ibn ‘Uthaymeen, part 2, p. 77-78)
In practical terms, we see that the saheeh Sunnah of the Prophet (peace and blessings of Allaah be upon him) prove that this myth is false, for the best of mankind, Muhammad (peace and blessings of Allaah be upon him), got married to the most beloved of people to him, namely ‘Aa’ishah (may Allaah be pleased with her), and his marriage to her took place between the two Eids, and she was one of the happiest of people with him. Indeed, she herself refuted this jaahili claim by saying, “The Messenger of Allaah (peace and blessings of Allaah be upon him) married me in Shawwaal and he consummated the marriage with me in Shawwaal, and which of the wives of the Messenger of Allaah (peace and blessings of Allaah be upon him) was dearer to him than me?”
‘Urwah ibn al-Zubayr said: ‘Aa’ishah used to like marriages to be consummated in Shawwaal. (Narrated by Muslim, 1423)
This shows that it is mustahabb to arrange marriages, get married and consummate marriages in Shawwaal. Our companions stated that it is mustahabb, and they quoted this hadeeth as evidence. By saying this, ‘Aa’ishah intended to refute the practice and belief of the jaahiliyyah. What some of the common people believe nowadays, that it is disliked to arrange marriages, get married and consummate marriages in Shawwaal, is false and has no basis. This is one of the leftovers of the jaahiliyyah. They used to regard that as inauspicious because of the fact that the name Shawwaal carries connotations of lifting.
Sharh Muslim, 9/209
Ibn al-Qayyim said:
‘Aa’ishah the Mother of the Believers (may Allaah be pleased with her) regarded it as mustahabb for a woman to be married or the marriage to be consummated with her in Shawwaal. She said, “The Messenger of Allaah (peace and blessings of Allaah be upon him) only married me in Shawwaal, and which of his wives was more beloved to him than me?” even though the people regarded marriage in Shawwaal as inauspicious This is something which the believers who truly put their trust in Allaah and whose hearts truly find contentment with their Lord should resolve to do, those who know that what Allaah wills will happen and what He does not will will not happen, and that nothing will befall them except that which Allaah has decreed, and that no calamity will befall them except that which was already written in the Book before they were created, who know that they will inevitably come to that which has been decreed for them, which must inevitably happen to them. If they are superstitious, this will not ward off the decree from them, rather their superstition will be one of the main reasons why what they fear of the Divine will and decree will come to them. Thus their fear will be the means of bringing what they fear upon them. So according to the will and decree of Allaah, their weakness of faith will be the cause of what they dislike happening to them, so their bad omen is with themselves. But those who put their trust in Allaah, who delegate their affairs to Him, who know Him and His commands, their souls are more noble than that and their interests more sublime. Their trust in Allaah and their positive thoughts of Him give them power, strength and protection against the things which people regard as evil omens and about which they are pessimistic. They know that there is no omen [or no birds] except His, no good except His, there is no god but Him, and that the Creation and Command are His, the Lord of the Worlds.
Miftaah Daar al-Sa’aadah, 2/261
With regard to the second question, please see the answer to Question # 8907, and the ruling on celebrating Laylat al-Nusf min Sha’baan (the fifteenth of Sha’baan) in the Periodical Topics section of this website.