[Machine] Whoever fasts one day in Rajab, it is like fasting for a year. Whoever fasts seven days, the seven gates of Hell are shut against him. Whoever fasts eight days, the eight gates of Paradise are opened for him. Whoever fasts ten days, he does not ask God for anything except that He grants it to him. Whoever fasts fifteen days, a caller from heaven proclaims: “I have forgiven you what has passed, so begin your deeds anew; I have replaced your bad deeds with good deeds.” And whoever does more, God increases for him.

And in Rajab, Noah was carried in the Ark, and Noah fasted and commanded those with him to fast; and the Ark carried them for six months, until the end of that, on the tenth day of Muharram.  

"مَنْ صَامَ يَوْمًا مِنْ رَجَبٍ كانَ كَصِيَامِ سَنَة، وَمَن صَامَ سَبْعَةَ أَيَّامٍ غُلِّقَتْ عَنْهُ سَبْعَةُ أَبْوَاب جَهَنَّمَ، وَمَن صَامَ ثَمَانِيَةَ أَيَّامٍ فُتِّحَتْ لَهُ ثَمَانِيَةُ أَبْوَابِ الجَنَّةِ، وَمَنْ صَامَ عَشْرَةَ أَيَّامٍ لَمْ يَسْألِ اللهَ شَيئًا إِلا أَعْطَاهُ، وَمَن صَامَ خَمْسَةَ عَشَرَ يَوْمًا نَادَى مُنَادٍ مِنَ السَّمَاءِ: قَدْ غَفَرْتُ لَكَ مَا سَلَفَ، فَاسْتَأنِف العَمَلَ، قَدْ بَدَّلتُ سيئاتِكَ حَسَنَات، وَمَن زَادَ زَادَهُ اللهُ، وفِي رَجَبٍ حُمِلَ نُوح بِالسَّفِينة وَصَامَ نُوحٌ وَأَمَرَ مَنْ مَعَهُ أَنْ يَصُومُوا، وَجَرَت بِهِم السفِينَةُ سِتَّةَ أَشْهُر إِلَى آخِرِ ذَلِكَ لِعَشْر خَلَوْنَ مِن المُحَرمِ".