Sayyiduna Abu Ayyub Ansari (may Allah be pleased with him) narrates: The Noble Prophet (peace and blessings be upon him) used to perform four rak‘ahs after the sun had declined, and he used to say: "At the time of the sun’s decline, the gates of the heavens (the narrator is in doubt, perhaps these are the words) or the gates of Paradise are opened."
Hadith Referenceمسند الحميدي / 389
Hadith Gradingمحدثین:إسناده ضعيف
Hadith Takhrij«إسناده ضعيف : عبيدة هو ابن معتب الضبي ضعيف، وباقي رجالة ثقات، وقزعة هو ابن يحيي - وأخرجه ابن خزيمة في«صحيحه» برقم: 1214، والحاكم فى «مستدركه» ، برقم: 5994، وأبو داود فى «سننه» برقم: 1270، وابن ماجه في«سننه» برقم: 1157، والبيهقي فى «سننه الكبير»، برقم: 4651، وأحمد فى «مسنده» ، برقم: 24015، والطيالسي فى «مسنده» ، برقم: 598، وابن أبى شيبة فى «مصنفه»، برقم: 5992، والطحاوي فى «شرح معاني الآثار» ، برقم: 1966»
Narrated Abu Ayyub: The Prophet ﷺ said: The gates of heaven are opened for four rak'ahs containing no taslim (salutation) before the noon prayer. Abu Dawud said: Yahya bin Saeed al-Qattan said: If I were to narrate any tradition from Ubaidah, I would narrate this tradition. Abu Dawud said: Ubaidah is weak. Abu Dawud said: The name of the narrator Ibn Minjab is Sahm.
Shaykh Umar Farooq Saeedi
1270. Commentary: Shaykh al-Albani rahimahullah has declared this hadith to be "hasan," whereas the following hadith [1295] is, according to him, "sahih." In it, it is stated that the voluntary (nafl) prayers of the day and night are to be performed in sets of two rak‘ahs. Therefore, performing the sunnah and nafl prayers in sets of two rak‘ahs is the preferred and superior way. However, it is also permissible to perform four rak‘ahs with a single taslim (salutation).
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 1270