ENOfficial
Anas said that the Prophet (ﷺ) stood in humble supplication for a month and then gave it up. Abu Dawud and Nasa'i transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ أَنَسٍ: أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَنَتَ شَهْرًا ثُمَّ تَرَكَهُ. رَوَاهُ أَبُو دَاوُد وَالنَّسَائِيّ
sunnah.com