Did ‘Umar ibn Al-Khattaab, may Allaah be pleased with him, see the Devil? Why did not he strangle him?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu 'alyhi wa sallam, is His slave and Messenger.

It is proved in the Sunnah (Prophetic tradition) that the Prophet, sallallaahu ‘alayhi wa sallam, said that if Satan saw ‘Umar walking down a street, Satan would take another path. [Al-Bukhari and Muslim]

This incident of the strangling happened with the Prophet, sallallaahu ‘alayhi wa sallam. It was narrated on the authority of Abu Hurayrah that Satan came to the Prophet, sallallaahu ‘alayhi wa sallam, while he was praying, because he wanted to spoil the prayer for the Prophet, sallallaahu ‘alayhi wa sallam. Allaah The Almighty enabled the Prophet, sallallaahu ‘alayhi wa sallam, to hold him down and he wanted to tie him to one of the pillars of the mosque, but he did not do so because he remembered what Prophet Sulaymaan (Solomon) said (which means): {He said, "My Lord, forgive me and grant me a kingdom such as will not belong to anyone after me. Indeed, You are the Bestower."} [Quran 38:35] [Al-Bukhari]

This supplication of Prophet Sulaymaan   entails having control over Jinn and the devils. Thus, tying Satan to the pillar would mean the Prophet's, sallallaahu ‘alayhi wa sallam, control over  him, which was something only given to Prophet Sulaymaan (Solomon) and thus he, sallallaahu ‘alayhi wa sallam, refrained from tying him.

Allaah Knows best.