It is a notification between the call to prayer (adhan) and the establishment of prayer (iqamah), whether it is by saying "Hayya 'ala al-falah" (Come to success), or "Qad qāmatiṣ-ṣalāh" (The prayer has been established), or "Ṣalāh, ṣalāh" (Prayer, prayer), or by clearing the throat, or by calling out, or otherwise. The term "tathweeb" has been applied to the phrase: "Prayer is better than sleep"; as narrated by Anas, may Allah be pleased with him, who said: "Tathweeb was in the Fajr prayer when the muezzin said: 'Hayya 'ala al-falah', he would say: 'Prayer is better than sleep.'" In Sharh Ma'ani al-Athar 1: 137. And from Bilal, may Allah be pleased with him, the Prophet, peace be upon him, said: "Do not perform tathweeb in any prayer except in the Fajr prayer," in Sunan al-Tirmidhi 1: 378. Sheikh Shu'ayb said: Ahmad narrated it 6: 14, and al-Bayhaqi 1: 424 through Abu Israel from al-Hakam, and its chain is weak due to the weakness of Abu Israel and its interruption, but there are supporting narrations from Abu Mahdhura in Abu Dawood 500, in which the Prophet, peace be upon him, said to him: "If it is the morning, say: 'Prayer is better than sleep, prayer is better than sleep.'" Ibn Hibban authenticated it 289. And from Anas, he said: "It is Sunnah that when the muezzin says in the Fajr adhan: 'Hayya 'alaṣ-ṣalāh, Hayya 'ala al-falah', he says: 'Prayer is better than sleep.'" Narrated by al-Daraqutni p. 90, and al-Bayhaqi 1: 423, and authenticated by Ibn Khuzaymah 386, and al-Bayhaqi. Al-Bayhaqi narrated 1: 423 through Ibn 'Ajlan, from Nafi', from Ibn 'Umar, who said: "The first adhan after 'Hayya 'alaṣ-ṣalāh, Hayya 'ala al-falah' was: 'Prayer is better than sleep' twice," and the Hafiz deemed it good in al-Talkhis 1: 201. This is concluded from the margin of Tahdhib al-Kamal 3: 83. It is preferable for the muezzin at Fajr to perform tathweeb between the two adhan, as it is a time of sleep and negligence, so that people may awaken and attend the mosque. Imam al-Marghinani said in al-Hidayah 1: 41: "This is the tathweeb that the scholars of Kufa innovated after the era of the Companions, may Allah be pleased with them, due to the emergence of negligence in prayer matters." As narrated by Abu Bakrah, may Allah be pleased with him, he said: "I went out with the Messenger of Allah, peace be upon him, for the Fajr prayer, and he would not pass by a man except that he called him to prayer or nudged him with his foot," in Sunan Abu Dawood 1: 22. The later scholars have preferred tathweeb for all people in all prayers, as they observed the emergence of laziness and negligence in all prayers, so tathweeb is performed to increase the congregation, except in the Maghrib prayer; for it is disliked to sit between the two adhan, thus making tathweeb in it meaningless, and it remains as it was originally. See: Al-Wiqayah Q9/A, and Minh al-Ghaffar in Sharh Tanwir al-Absar Q1: 50/A, and Jam' al-Rumuz in Sharh al-Nuqayah 1: 78, and the Hashiyah of al-Tahtawi on al-Durr al-Mukhtar Sharh Tanwir al-Absar 1: 186, and Durar al-Hukam Sharh Gharar al-Ahkam 1: 56, and Sharh Abi al-Makarim on al-Nuqayah Q26/A, and Sharh Ibn Malik on al-Wiqayah Q23/A, and Kamal al-Darayah in Sharh al-Nuqayah Q34/B, and Rad al-Muhtar on al-Durr al-Mukhtar 1: 261.