In other words, since the spiritual illumination of wahi and the noor of the angel suddenly descended upon the human body of Rasulullah (sallallahu ‘alaihi wasallam), due to the magnitude of the wahi, he felt that if the intensity of this wahi continues in this manner, his human body will be unable to withstand the weight of the wahi. It could also mean that he thought he would perish under the weight of prophethood.

The following verse indicates to the weight and great responsibility of wahi:

اِنَّا سَنُلۡقِیۡ عَلَیۡکَ قَوۡلًا ثَقِیۡلًا ﴿۵﴾

“We will reveal upon you a very weighty word.” [Surah Muzzammil v. 5]

(Extracted from Seeratul Mustafa 1/136)