Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(Lo! now they) i.e. Akhnas Ibn Shurayq and his followers (fold up their breasts) conceal in their hearts their hatred and enmity for Muhammad (pbuh) (that they may hide from him) that they may hide from Muhammad (pbuh) their hatred and enmity by keeping his company and pretending to him that they love him. (At the very moment when they cover themselves with their clothing) at the moment they cover their heads with their clothes, (Allah knoweth that which they keep hidden) among themselves as well as that which they conceal in their hearts (and that which they proclaim) of fighting and antipathy; it is also said that this refers to that which they proclaim of love and keeping company. (Lo! He is Aware of what is in the breasts (of men)) whether it is good or evil.
As reported by al-Bukhārī [by way of an isnād] from Ibn ‘Abbās, the following was revealed regarding those who were embarrassed to withdraw [to relieve nature] or to have sexual intercourse [without their clothes] and become exposed to the heaven. It is also said: [that it was revealed] regarding the hypocrites: Lo!, they fold up their breasts that they may hide from Him, that is, [from] God; lo! the moment they cover themselves with their garments, wrapping themselves up therewith, He, God, exalted be He, knows what they keep hidden and what they proclaim, and so their hiding is to no avail. Truly He knows what is in the breasts [of men], that is, what is in the hearts.
Ibn `Abbas said, "They used to dislike facing the sky with their private parts, particularly during sexual relations. Therefore, Allah revealed this verse.'' Al-Bukhari recorded by way of Ibn Jurayj, who reported from Muhammad bin `Abbad bin Ja`far who said, "Ibn `Abbas recited, (أَلَا إِنَّهُمْ تَثْنَونِي صُدُورُهُمْ) "Behold their breasts did fold up.'' So I said: `O Abu Al-`Abbas! What does -their breasts did fold up- mean' He said, `The man used to have sex with his woman, but he would be shy, or he used to have answering the call of nature (in an open space) but, he would be shy. Therefore, this verse,
أَلا إِنَّهُمْ يَثْنُونَ صُدُورَهُمْ
(No doubt! They did fold up their breasts,) was revealed.''' In another wording of this narration, Ibn `Abbas said, "There were people who used to be shy to remove their clothes while answering the call of nature in an open space and thus be naked exposed to the sky. They were also ashamed of having sexual relations with their women due to fear of being exposed towards the sky. Thus, this was revealed concerning them.'' Al-Bukhari reported that Ibn `Abbas said that
(they cover themselves) means that they cover their heads.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
They were those people of Makkah, who though not very active in their antagonism against the Message of the Holy Prophet, nevertheless were very averse to it. Therefore they did not like to hear it nor come face to face with him, and did their very best to avoid him. If, by chance, they found him sitting somewhere and talking to the people, they would at once turn back on their heels. Or if they saw him coming towards themselves they would slink away or hide their faces with cloth for fear that he might address them and convey his Message to them. As they did not have the courage to face the. Truth, they would bury their heads ostrich-like and make believe that the Reality from which they were hiding had disappeared, whereas it was all along there and watching their ridiculous attempts to hide from it.
That is, "It is foolish on your part to deceive yourselves that you can escape punishment by hiding yourselves from Allah Who has full and perfect. knowledge of everything: Who knows the nest where the tiniest sparrow lives and the hole where the smallest insect resides, and provides their sustenance to them wherever they be: Who knows the dwelling place and the final resting place of every creature and gives life and death to them at the appointed time. Do you think that by hiding yourselves from His Messenger, you can also hide yourselves from the All-Knowing Sovereign Who has sent him? Do you think that Allah does not see His Messenger doing his very best to convey His Message to you and you are trying to turn a deaf ear to it?"
(Lo! now they fold up their breasts that they may hide (their thoughts) from Him…) [11:5]. This verse was revealed about al-Akhnas ibn Shurayq who was good looking and sweet talking. When he met the Messenger of Allah, Allah bless him and give him peace, he pleased him but he always kept in his heart that which displeased him. Al-Kalbi said: “He used to sit with the Prophet, Allah bless him and give him peace, and display things that pleased the Prophet while hiding in his heart the opposite of what he displayed. And so Allah, exalted is He, revealed (Lo! now they fold up their breasts that they may hide (their thoughts)) their thoughts of enmity to Muhammad, Allah bless him and give him peace”.