“Allah has sent down from the heavens to the earth four blessed things: Iron, fire, water and salt.” what is the meaning of heaven here?
…………………………………………..

This is a fabricated hadeeth and it is a lie.

Imam ad-Daylamy in “ al-Firdaws ” , Imam as-Siuti in “ Jam’al-Jawami ” , Ibn Kathir in “ al-Kafi ash-Shafi fi Takhrij Ahadith al-Kash-shaf’ Imam al-Agluni in “ Kashf al-Khafa ” and Imam al-Qurtubi in his “ Tafsir ” reported that the Prophet (PBUH) said:

Hadeeth & its Sciences | February 24, 2014 2:17 am
Previous

In a Hadith Jibree (as) made the following du’a: “Destruction to him before whom thy name is taken and then he does not make Dua for Allah’s blessing on you (by saying sal Allahu aleihi wa sallam for example). June 16, 2012 – 20:36 — contribute Since I’ve learned that sending blessing on our Prophet (sal Allahu aleihi wa sallam) when his name is mentioned is not wajib then why did Jibreel (as) say this dua (for destruction)?
Next

“Purify these Bodies (of yours), May Allah grant you purity, for indeed there is not a servant that spends the night in a state of purification except that an angel spends the night with him in his hair. He does not turn at anytime during the night