السلام عليكم ورحمة الله وبركاته Ustadh, Do we need to sleep after Isha in order to pray Tahajjud, or is sleep not necessary? And is it true that the most rewarded time for Tahajjud is the last third of the night?

Ustadh AbdulAziz al-Haqqan

Not necessary, but the best is after sleeping and waking up at the last 3rd of the night to do it. But if u pray tahajud straight after isha, it is allowed as well.