Regarding the prohibition on interlacing the fingers during prayer and before the prayer and immediately after it, there is a hadith which was narrated via Sa`id al-Maqburi, from whom a number of narrators narrated it.
Muhammad ibn `Ajlan narrated it from him, but the ones who narrated from him narrated the hadith inconsistently and with differences in its chain of narration.
Ibn Khuzaymah (may Allah have mercy on him) said:
As for Ibn `Ajlan, he was confused and muddled in his chain of narration. Sometimes he said “from Abu Hurayrah”, sometimes he narrated it as a mursal report [without mentioning the name of the Sahabi], and sometimes he said “from Sa`id, from Ka`b.”
End quote from Sahih Ibn Khuzaymah, 1/277.
Ibn Abi Dhi’b and Sa`d ibn Is-haq narrated it from al-Maqburi with different chains of narration from both of them.
Abu Mash`ar Nujayh ibn `Abd ar-Rahman also narrated it from al-Maqburi, but he was classed as weak, and his chain of narration includes some whose names were unknown.
It was also narrated from al-Maqburi from Abu Thumamah, but his status is unknown.
Adh-Dhahabi (may Allah have mercy on him) said:
It was narrated by a number of narrators from al-Maqburi, from Abu Thumamah, whose status is unknown and he is only mentioned in this hadith, in which there is some oddness.
End quote from Al-Muhadhdhab fi Ikhtisar as-Sunan al-Kabir, 3/1160.
But it was also narrated by a trustworthy narrator from al-Maqburi, as ad-Darimi (1446) and Ibn Khuzaymah (446) narrated it via Muhammad ibn Muslim.
Ibn Khuzaymah (447) and al-Hakim (1/206) also narrated it via `Abd al-Warith ibn Sa`id.
Both Muhammad ibn Muslim and `Abd al-Warith ibn Sa`id narrated it from Isma`il ibn Umayyah, from Sa`id al-Maqburi, from Abu Hurayrah, who said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever does wudu’ then sets out intending to pray is in a state of prayer until he returns to his house, so do not do like this” – meaning interlacing the fingers.
Al-Hakim said: This hadith is authentic according to the conditions of al-Bukhari and Muslim, although they did not narrate it. And adh-Dhahabi agreed with him.
In addition to the various chains of narration for this hadith, there are also some differences in its text. Some versions of the hadith were narrated without the phrase “until he returns to his house.”
There is a report which is more authentic, and which indicates that it is permissible to interlace the fingers after finishing the prayer. It was narrated that Abu Hurayrah said: The Messenger of Allah (blessings and peace of Allah be upon him) led us in praying one of the two afternoon prayers [Zuhr or `Asr] – Ibn Sirin said: Abu Hurayrah named it, but I have forgotten –. He said: He led us in praying two rak`ahs, then he said the taslim. Then he got up and went to a horizontal beam in the mosque and leaned against it, as if he was angry. He put his right hand over his left hand and interlaced his fingers, and he rested his right cheek on the back of his left hand. Those who were in a hurry left through the doors of the mosque, and [the people] wondered whether the prayer had been shortened. Among the people were Abu Bakr and ‘Umar, but they could not speak, out of respect [for the Prophet (blessings and peace of Allah be upon him)]. Also among the people there was a man with long arms who was called Dhul-Yadayn [He with the arms]. He said: O Messenger of Allah, did you forget or has the prayer being shortened?
He said: “I did not forget and it has not been shortened.”
Then he said: “Is what Dhul-Yadayn said true?” They said: Yes. So he went forward and prayed what he had omitted, then he said the taslim, then he said takbir and prostrated as he usually did, or for longer. Then he raised his head and said takbir, then he said takbir and prostrated as he usually did, or for longer. Then he raised his head and said takbir. Perhaps they asked him [the narrator]: Then did he say the taslim? and he said: I was told that `Imran ibn Husayn said: Then he said the taslim. Narrated by al-Bukhari, 482. The basic principle according to the scholars is to reconcile between the texts as much as possible, and in order to reconcile between all these texts we may say that interlacing the fingers is disallowed when going to pray and waiting to pray, but once the prayer is over, it is permissible to interlace the fingers.
Ibn Rajab (may Allah have mercy on him) said:
Abu Bakr al-Isma`ili stated in his book As-Sahih al-Mukhraj `ala Sahih al-Bukhari: The hadith of Ka`b ibn `Ujrah and similar reports do not contradict the hadith of Abu Hurayrah which al-Bukhari narrated concerning this topic, and it is possible to reconcile between them by noting the following:
It is only disliked to interlace the fingers for one who is praying or who comes under the same ruling as one who is praying, such as one who is walking to the mosque or is sitting in the mosque and waiting for the prayer.
As for the one who has finished his prayer and has got up, as the Prophet (blessings and peace of Allah be upon him) did when he said the taslim following two rak`ahs, then he got up and went to a horizontal beam, and at that time he had finished praying and was not waiting for the prayer, so it did not matter that he interlaced his fingers at that moment.
End quote from Fat-h al-Bari, 3/423.
`Ala’ ad-Din Mughaltay (may Allah have mercy on him) said:
If it were to be said: It is narrated in As-Sahih in the reports about the day of Dhul-Yadayn that the Prophet (blessings and peace of Allah be upon him) placed his right hand over his left hand and interlaced his fingers,
the response to that is that he did that after he had finished praying, so there is no contradiction. And Allah knows best.
Regarding the hadith of Ibn `Umar or Ibn `Amr that was narrated by al-Bukhari, according to which the Prophet (blessings and peace of Allah be upon him) interlaced his fingers, and the hadith of Abu Musa which was also narrated in a marfu` report by al-Bukhari, and which says “The believers are like a structure, parts of which support other parts”– and he interlaced his fingers, that happened outside of the prayer.
End quote from Sharh Sunan Ibn Majah, 5/1621.
Shaykh Ibn `Uthaymin (may Allah have mercy on him) said:
Interlacing the fingers, for one who is going to the prayer, or is sitting in the mosque waiting for the prayer, or is praying, is not allowed and it is regarded as bad manners.
However, at other times there is nothing wrong with it, so it is permissible for a person to interlace his fingers after the prayer, because it is soundly narrated that the Prophet (blessings and peace of Allah be upon him) did that. That was when he said the taslim in one of the two afternoon prayers, either Zuhr or `Asr, before he had completed his prayer. Then he went to a horizontal beam in the mosque and leaned on it, and interlaced his fingers.
What some people think, that interlacing the fingers is disallowed at all times, is wrong. It is soundly narrated from the Prophet (blessings and peace of Allah be upon him) that he said: “The believers are like a structure, parts of which support other parts” – and he interlaced his fingers.
End quote from Fatawa Nur `ala ad-Darb, 4/340.
Thinking of it, we realize that in order to reconcile the reports, we should understand it in this manner; interlacing the fingers is disallowed because of the prayer, so the prohibition is restricted to prayer and the preparations that come before the prayer.
Al-Khattabi (may Allah have mercy on him) said:
Interlacing the fingers is something that some people do by way of fidgeting, and some of them do it to crack the knuckles when they want to stretch them. Perhaps a person may sit with his legs drawn up to his chest and his arms around them, clasping his hands with his fingers interlaced, and he may be overcome by sleep in that position, which could lead to him breaking his wudu’. Hence it should be said to one who purifies himself and sets out heading to the mosque to pray: Do not interlace your fingers, because none of the various reasons that we have mentioned above are appropriate for prayer and they are not appropriate for one who is praying.
End quote from Ma`alim as-Sunan, 1/162.
And Allah knows best.