Is it better to delay the 'Ishā' prayer, and did the Prophet delay it then sleep, and why do people pray it in mosques shortly after the adhān?

Delaying the 'Isha prayer is commendable, as stated in several prophetic traditions, such as the Prophet's (peace be upon him) own actions and his saying, "Were it not that I would overburden my Ummah, I would have commanded them to delay the 'Isha prayer until one-third or half of the night." There is also Aisha's narration about his delaying the 'Isha prayer one night.

However, delaying it is disliked if it causes hardship to the worshipers or leads to missing the congregational prayer. Praying it at the beginning of its time with the congregation is better, as mentioned by Ibn Qudamah and Ibn Taymiyyah.

The Prophet (peace be upon him) did not always delay it; rather, he sometimes prayed it at the beginning of its time, out of consideration for the congregants.