Is it permissible to recite Ayat (verse) al-kursi in one Rak’ah of Salah? Ayat al-kursi consists of only one Ayat and I have heard that one should recite at least three verses from the holy Quran in one Rak’ah of his prayer. If someone reads only the Ayat al-kursi in one Rak’ah of his prayer, does he have to repeat the prayers or not?
Thank you.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

All the jurists are agreed that Al-Faatihah is the only part of the Quran that is obligatory in prayer. So, any other part of Quran you read after Al-Faatihah is Sunnah. So, the praying person is rewarded for acting according to the Sunnah but his prayer is not nullified if he misses to read some Quran after Al-Faatihah.

Some scholars believe that the person who does not read (or forgets to read) some Quran after Al-Faatihah, should perform two prostrations for forgetfulness.

On the other hand, there is evidence that reading one verse after Al-Faatihah is sufficient. Al-Daaraqutni reported from Ibn ‘Abbas that “He read Al-Faatihah and one Ayah (verse) from Chapter Al-Baqarah in each Rak'ah.”

So, your prayer is valid and you comply with the Sunnah if you read some Quran in addition to Al-Faatihah (one verse or more).

Allah knows best.