Whoever performed Witr at the Start of the Night, then stood in Prayer at the End of it
Question :
If I performed Witr at the start of the night, then I stood in prayer at the end of the night, how should I pray?
Answer:
If you performed Witr at the start of the night, then Allah made it easy for you to stand in prayer at the end of the night, pray whatever Allah makes easy for you in units of two Rak'ahs without Witr, in accordance with the words of the Prophet:
There cannot be two Witr prayers in one night.
And the Hadith authentically reported from 'A'ishah, may Allah be pleased with her, in which she said that the Prophet used to pray two Rak'ahs after Witr while he was sitting. And the wisdom behind that - and Allah knows best - was to inform the people of the permissibility of praying after Witr.
Source:
Ibn Baz
Fatawa Islamiyah, Vol. 2 Pages