It is narrated from Hazrat Amr bin Abasah (may Allah be pleased with him) that the Holy Prophet (peace and blessings of Allah be upon him) said: The night prayer should be performed in sets of two rak'ahs, and supplication is most accepted in the last part of the night.
Hadith Referenceمسند احمد / تتمہ مُسْنَدِ الْكُوفِيِّينَ / 19449
Hadith Gradingحکم دارالسلام:بعضه صحيح، و بعضه الآخر صحيح لغيره، وهذا إسناد ضعيف، راجع ماقبله