Narrated by Abu Said, the freed slave of Bani Hashim, narrated by Imran Abu Awwam , from Qatada , from Abu Maleeh , from Waathilah bin Asqa that the Messenger of Allah, peace and blessings be upon him, said:
“The suhufs of Abraham, upon him be peace, were revealed on the first night of Ramadan. The Torah was revealed after six nights of Ramadan had passed. The Gospel was revealed after thirteen nights of Ramadan had passed. The Furqan (Al Qur’an) was revealed after twenty four nights of Ramadan had passed.” 1
According this Hadith which is also cited by ibn Kathir in his tafseer on Qur’an 2:185; Ramadan is a very special month because this one month in the Islamic lunar calendar was the same month when the all the four sacred scriptures to four special Prophets: Abraham, Moses, Jesus and Muhammad. were revealed in the month of Ramadan.
While I have not yet looked into how we would understand the revelation of the Injil on the thirteenth day of Ramadan, but interestingly Ramadan is the ninth month of the Islamic calendar and the Shavuot , a major Jewish festival for commemorating the revelation of the Torah is held on the month of Sivan which is also the ninth month of the Hebrew calendar (2).
From this hadith we learn that all revelation from God actually occurred in the same lunar month, but because the Jews, who also use the lunar calendar have modified the length of the year with a leap month seven times in every nineteen year cycle, so as to always keep the the ancient Jewish Hajj: the Sukkot in the fall season, they do not coincide. But every nine or ten times in a solar century Ramadan and Sivan will overlap. This happens this year, Nuzul Al Qur’an (the revelation of the Qur’an) will be celebrated at the same time as Nuzul At Tawraat (the revelation of the Qur’an or Shavuot as it is known to the Jews). Muslims and Jews throughout the world will rejoice at the same time.
أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ : أُنْزِلَتْ صُحُفُ إِبْرَاهِيمَ عَلَيْهِ السَّلَامُ فِي أَوَّلِ لَيْلَةٍ مِنْ رَمَضَانَ ، وَأُنْزِلَتِ التَّوْرَاةُ لِسِتٍّ مَضَيْنَ مِنْ رَمَضَانَ ، وَالْإِنْجِيلُ لِثَلَاثَ عَشْرَةَ خَلَتْ مِنْ رَمَضَانَ ، وَأُنْزِلَ الْفُرْقَانُ لِأَرْبَعٍ وَعِشْرِينَ خَلَتْ مِنْ رَمَضَانَ Musnad Ahmad ibn Hanbal 16727