(a) It is narrated from Sayyiduna al-Nu'man bin Bashir (may Allah be pleased with him): I know better than anyone when the time of the Isha prayer is.
The Messenger of Allah (peace and blessings be upon him) used to offer the Isha prayer when the moon of the third night had set.
(b) All the narrations about offering the prayers early in general have already been mentioned.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2111