Is it permissible to delay the 'Isha prayer until an hour before Fajr to encourage performing the night vigil (Qiyam al-Layl)?

Delaying the Isha prayer until an hour before Fajr, which involves sleeping before it, is Islamically disliked (makrooh). It also necessitates delaying the prayer until its time of necessity. Delaying Isha for the purpose of performing Tahajjud is not justified, because the most beloved deeds to Allah are the obligatory ones. A Muslim can be diligent in performing Tahajjud at the end of the night, or at its beginning if waking up at the end of the night is difficult for them.