When is the prostration of forgetfulness (sujud al-sahw) before the tasleem and when is it after, and what is the ruling on one who prays 'Isha with Fajr?

"Scholars of Islamic jurisprudence differ on the timing of the prostration of forgetfulness (sujood al-sahw). Some, like Al-Shafi'i, hold that it should be performed before the salutations (tasleem). Others, like Abu Hanifa, maintain it should be performed after. Malik differentiated, stating that if the cause was a deficiency, it is performed before the salutations, and if it was an addition, it is performed after. As for Ahmad, he held it should be performed before the salutations, except for cases explicitly mentioned in texts as being after the salutations.

Regarding someone who prays 'Isha with Fajr: if it is after the dawn has broken, he prays 'Isha as a make-up (qada') then Fajr as a timely performance (ada'). If it is before the dawn has broken, he prays 'Isha as a timely performance (ada'). It is not permissible to pray Fajr before its prescribed time. And whoever deliberately and negligently delays 'Isha until after dawn breaks is sinful."