الرُّوحُ : He is Sayyiduna Jibril (May peace be upon him) as mostly said. Allah (swt) says:
﴾نَزَلَ بِهِ الرُّوحُ الْأَمِينُ % عَلَىٰ قَلْبِكَ لِتَكُونَ مِنَ الْمُنذِرِينَ﴿
(The Trustworthy Spirit has brought it down % Upon your heart, [O Muhammad] – that you may be of the warners -) (Ash-Shu’araa: 193-194)