What should be the length of the Surah recited after Surah Fatihah in Salaah?

Reciting verses after the Fatihah is something recommended and to the best of my understanding even a single verse will suffice. Some scholars have made it a condition that the verse must be a long one and not a short one, some have said that it has to be at least three.

From this we can say the minimum will be one verse but to be in the safest position is to recite at least three after all we will get the reward for reciting more from the verses of the Qur’an. [1]

Reference:

[1] Sheikh S Al-Fawzan, A Summary of Islamic Jurisprudence, 1/129