The correct view with regard to this question is that it is permissible to sit either cross-legged or to sit muftarishan (kneeling with the left foot tucked under the buttocks and the right foot vertical), because nothing has been narrated concerning that from the Messenger of Allaah (peace and blessings of Allaah be upon him).
‘Aa’ishah (may Allaah be pleased with her) narrated that the Prophet (peace and blessings of Allaah be upon him) prayed sitting down, but she did not describe how he sat, which indicates that there is some room for manoeuvre in this matter.
Imaam al-Shaafa’i (may Allaah have mercy on him) said: It is permissible to sit in whatever manner the worshipper wishes.
Imaam Ibn al-Mundhir said in al-Awsat (4/376): With regard to how the person who is praying sitting down should sit, there is no Sunnah to be followed. Since that is the case, the person who is sick may pray sitting in whatever manner is easy for him; if he wishes he may pray sitting cross-legged and if he wishes he may pray sitting with his legs drawn up, and if he wishes he may pray sitting as one sits between the two prostrations. All of that was narrated from earlier scholars.
A group of scholars said that sitting cross-legged is preferable. This was narrated from Ibn ‘Umar and Anas ibn Maalik, and this is the view of Abu Haneefah, Maalik and Ahmad.
The evidence they quote is the report narrated by al-Nasaa’i (3/376) and others via Abu Dawood al-Hafari from Hafs from Humayd from ‘Abd-Allaah ibn Shaqeeq from ‘Aa’ishah who said: “I saw the Prophet (peace and blessings of Allaah be upon him) pray sitting cross-legged.”
But this hadeeth is not saheeh and it was narrated from more than one source that there is nothing that mentions sitting cross-legged. Al-Nasaa’i (may Allaah have mercy on him) said: I do not know of anyone who narrated this hadeeth apart from Abu Dawood and he is thiqah (trustworthy); I do not think that this hadeeth is sound.
Imam Ibn al-Mundhir said in al-Awsat (4/376): there are some suspicions about the isnaad of the hadeeth of Hafs ibn ‘Ghiyaath. A group narrated this hadeeth from ‘Abd-Allaah ibn Shaqeeq but it makes no mention of sitting cross-legged, and I do not think that this hadeeth can be proven to be attributed to the Prophet (peace and blessings of Allaah be upon him).
It was narrated from ‘Abd-Allaah ibn Mas’ood that he regarded praying sitting cross-legged as makrooh. This was narrated by Ibn Abi Shaybah and Ibn al-Mundhir.
It was narrated from Ahmad in one report that if the recitation is lengthy, one may sit cross-legged, otherwise one should sit muftarishan.
The correct view is the first one, which is that one has the choice of either sitting cross-legged, or sitting muftarishan.