Praise be to Allah.
It was narrated that Sahl ibn Sa’d said: the people used to be instructed to place the right hand over the left forearm when praying. (narrated by al-Bukhaari, no. 740)
It was narrated from Ibn ‘Abbaas (may Allaah be pleased with him) that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “We Prophets have been commanded to delay our suhoor and to break our fast straight away, and to place our right hands over our left hands when praying.” (narrated by Ibn Hibbaan in al-Saheeh, 3/13-14).
From these two ahaadeeth it is clear to us that the one who puts his hands by his sides in prayer is making a mistake. Putting the right hand over the left hand is the teaching of our Prophet (peace and blessings of Allaah be upon him) and of the Prophets who came before him.
(See Zaad al-Ma’aad, 1/202)
Ibn ‘Abd al-Barr said:
Nothing to the contrary has been narrated from the Prophet (peace and blessings of Allaah be upon him), and this is the view of the majority of the Sahaabah and Taabi’een. This is what was mentioned by Maalik in al-Muwatta’, and Ibn al-Mundhir and others did not narrate any differing view from Maalik… (See al-Fath, 2/224; Nayl al-Awtaar, 2/201)
The Maalikis said, concerning the report about holding one hand with the other in fard and naafil prayers, that this is the more correct meaning, because people were commanded to do this during the earliest generations (See al-Qawaaneen, 65).
What is well-known from the later books of the Maalikis is that it is recommended for the worshipper to place the hands below the chest and above the navel, in both naafil and fard prayers. If a person does this with the intention of following the Sunnah, or with no specific intention,this is fine, but if his intention is to lean on his hands or find a more comfortable position by putting one hand on top of the other, then this is makrooh.
Al-Baaji, one of the prominent Maalikis, said: “It may be that Maalik said that placing one hand on top of the other is makrooh because he was afraid that the common people would believe that this was one of the esential pillars of the prayer and that prayer would be invalid if one did not do this.”
Anyone who thinks about this matter will realize for certain that they all acknowledge that the Sunnah of the Prophet (peace and blessings of Allaah be upon him) is for the worshipper to place his hands on his front, not to hold them by his sides. Whatever Imaam Maalik said about holding the hands by one's side – if indeed the reports from him are saheeh – was only to counteract an action that was not prescribed in the Sunnah, which was leaning on the hands, or an incorrect belief, i.e., the belief of the common people that this was obligatory. It was said that when Maalik (may Allaah have mercy on him) refused to accept the position of qaadi (judge), he was beaten, and he could not put his hands on his chest when praying, so he held them by his sides because of the pain. Some of those who saw that thought this was Sunnah so they transmitted this from him. But he (may Allaah have mercy on him) definitely did not say that the arms should be held by one’s side at all. This is a misunderstanding of some written statement and it goes against what he stated clearly in al-Muwatta’ about the right hand being placed on top of the left. This was explained by a group of Maalikis and others, in various books which number approximately thirty, apart from what is mentioned in various commentaries.
Moreover, if it were proven that Maalik did hold his arms by his side for no reason, which is more deserving of being followed, the actions and words of the Prophet (peace and blessings of Allaah be upon him), as mentioned in the ahaadeeth quoted above, or the words of Imaam Maalik?
Every seeker of the truth will follow the Sunnah of Muhammad (peace and blessings of Allaah be upon him) and give it priority over the views of anyone else.
And Allaah knows best.