Al-Bukhari recorded in his Tafsir of this Ayah that `Abdullah bin Mas`ud said, "While I was walking with the Prophet on a farm, and he was resting on a palm-leaf stalk, some Jews passed by. Some of them said to the others, `Ask him about the Ruh.' Some of them said, `What urges you to ask him about that' Others said, `Do not ask him, lest he gives you a reply which you do not like.' But they said, `Ask him.' So they asked him about the Ruh. The Prophet kept quiet and did not give them an answer, and I knew that he was receiving revelation, so I stayed where I was. When the revelation was complete, the Prophet said:
وَيَسْـَلُونَكَ عَنِ الرُّوحِ قُلِ الرُّوحُ مِنْ أَمْرِ رَبِّى
(And they ask you concerning the Ruh (the spirit). Say: "The Ruh (the spirit) is one of the things, the knowledge of which is only with my Lord...") This context would seem to imply that this Ayah was revealed in Al-Madinah, and that it was revealed when the Jews asked him this question in Al-Madinah, although the entire Surah was revealed in Makkah. This may be answered with the suggestion that this Ayah may have been revealed to him in Al-Madinah a second time, after having previously been revealed in Makkah, or that he was divinely inspired to respond to their question with a previously-revealed Ayah, namely the Ayah in question. Ibn Jarir recorded that `Ikrimah said, "The People of the Book asked the Messenger of Allah ﷺ about the Ruh, and Allah revealed:
وَيَسْـَلُونَكَ عَنِ الرُّوحِ
(And they ask you concerning the Ruh...) They said, `You claim that we have only a little knowledge, but we have been given the Tawrah, which is the Hikmah,
وَمَن يُؤْتَ الْحِكْمَةَ فَقَدْ أُوتِىَ خَيْرًا كَثِيرًا
(and he, to whom Hikmah is granted, is indeed granted abundant good.)' 2:269 Then the Ayah
وَلَوْ أَنَّمَا فِى الاٌّرْضِ مِن شَجَرَةٍ أَقْلاَمٌ وَالْبَحْرُ يَمُدُّهُ مِن بَعْدِهِ سَبْعَةُ أَبْحُرٍ
(And if all the trees on the earth were pens and the sea (were ink wherewith to write), with seven seas behind it to add to its (supply),) 31:27 was revealed. He said, "Whatever knowledge you have been given, if Allah saves you from the Fire thereby, then it is great and good, but in comparison to the knowledge of Allah, it is very little."
وَيَسْـَلُونَكَ عَنِ الرُّوحِ
(And they ask you concerning the Ruh.) Al-`Awfi reported that Ibn `Abbas said, "This was when the Jews said to the Prophet , `Tell us about the Ruh and how the Ruh will be punished that is in the body - for the Ruh is something about which only Allah knows, and there was no revelation concerning it.' He did not answer them at all, then Jibril came to him and said:
قُلِ الرُّوحُ مِنْ أَمْرِ رَبِّى وَمَآ أُوتِيتُم مِّن الْعِلْمِ إِلاَّ قَلِيلاً
(Say: "The Ruh (the spirit) is one of the things, the knowledge of which is only with my Lord. And of knowledge, you (mankind) have been given only a little.") So the Prophet told them about that, and they said, `Who told you this' He said,
«جَاءَنِي بِهِ جِبْرِيلُ مِنْ عِنْدِ الله»
(Jibril brought it to me from Allah.) They said, `By Allah, no one has told you that except our enemy i.e., Jibril.' Then Allah revealed:
قُلْ مَن كَانَ عَدُوًّا لِّجِبْرِيلَ فَإِنَّهُ نَزَّلَهُ عَلَى قَلْبِكَ بِإِذْنِ اللَّهِ مُصَدِّقًا لِّمَا بَيْنَ يَدَيْهِ
(Say: "Whoever is an enemy to Jibril (let him die in his fury), for indeed he has brought it (this Qur'an) down to your heart by Allah's permission, confirming what came before it.)" 2:97
As-Suhayili mentioned the dispute among the scholars over whether the Ruh is the same as the Nafs, or something different. He stated that it is light and soft, like air, flowing through the body like water through the veins of a tree. He states that the Ruh which the angel breathes into the fetus is the Nafs, provided that it joins the body and acquires certain qualities because of it, whether good or bad. So then it is either a soul in (complete) rest and satisfaction (89:27) or inclined to evil (12:53), just as water is the life of the tree, then by mixing with it, it produces something else, so that if it mixes with grapes and the grapes are then squeezed, it becomes juice or wine. Then it is no longer called water, except in a metaphorical sense. Thus we should understand the connection between Nafs and Ruh; the Ruh is not called Nafs except when it joins the body and is affected by it. So in conclusion we may say: the Ruh is the origin and essence, and the Nafs consists of the Ruh and its connection to the body. So they are the same in one sense but not in another. This is a good explanation, and Allah knows best. I say: people speak about the essence of the Ruh and its rulings, and many books have been written on this topic. One of the best of those who spoke of this was Al-Hafiz Ibn Mandah in a book which we have heard about the Ruh.
وَلَئِن شِئْنَا لَنَذْهَبَنَّ بِالَّذِى أَوْحَيْنَا إِلَيْكَ ثُمَّ لاَ تَجِدُ لَكَ بِهِ عَلَيْنَا وَكِيلاً