Wa-itha raaytahum tuAAjibuka ajsamuhum wa-in yaqooloo tasmaAA liqawlihim kaannahum khushubun musannadatun yahsaboona (surah Munafiqun: 4)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(63:4) When you look at them, their persons are pleasing, and when they speak, you pay heed to what they say. *5 But in truth they are (merely) beams of timber propped-up (against a wall). *6 They consider every shout they hear to be directed against them. *7 They are your utter enemies; *8 guard against them. *9 May Allah do away with them! *10 How are they being turned away (from the Truth)? *11

Wa izaa ra aytahum tu`jibuka ajsaamuhum wa iny yaqooloo tasma` liqawlihim kaannahum khushubum musannadah; yahsaboona kulla saihatin `alaihim; humul `aduwwu fahzarhum; qaatalahumul laahu annaa yu`fakoon

*5) Hadrat 'Abdullah bin 'Abbas has stated that 'Abdullah bin Ubayy WAS a strongly built, healthy, handsome and smooth-tongued person, and the same was the case will most .of his companions. They were aII the nobles of Madinah. When they came to sit in the Holy Prophet's assembly, they would sit reclining on cushions against the walls and would talk agreeably and convincingly. From their outward appearance and manner of speech no one could imagine that those honourable people of the city would be so wretched and degraded in their character.
*6) That is, "Those who sit reclining on cushions against the walls, are not nun but pieces of timber. Comparing them to timber is meant to imply that they are devoid of the moral sense which is the essence of humanity Then by comparing them to blocks of timber propped up against the walI, it has also been pointed out that they are absolutely worthless, for the timber would be useful only when it has been utilized in making of a ceiling, or a doorframe, or a piece of furniture. A block of timber that has just been placed against a walI serves no useful purpose at all. "
*7) This brief sentence portrays the state of their guilty conscience. Since they fully well knew what game of hypocrisy they were playing tinder the screen of their superficial faith, they always remained in a state of alarm, thinking as to when the secret of their treason might be exposed, or the believers might feel disgusted with their evil deeds and machinations and take them co task for them. If ever a cry was raised anywhere in the city, or a noise was heard; they inunediately grew alarmed and thought it was directed against themselves.
*8) In other words, these hidden enemies arc more dangerous than the open enemies.
*9) That is, "Do not be deceived by their outward appearances. Beware of them, for they can deceive you any moment. "
*10) This is not a curse but a declaration of the verdict about them by Allah that they have become worthy of His punishment and He will certainly inflict His punishment on them. It is also possible that AIIah may not have used these words in their literal sense but in the meaning of a curse and condemnation according to Arabic idiom.
*11) It has not been pointed out as to who perverts them from belief to hypocrisy. This by itself makes it clear that there is not one but manu factors responsible for their perversion. There is Satan, there are their evil friends, and there are their own selfish motives. Someone's wife or children become his motive, and someone is driven to perversion by the evil ones in his society, or by jealousy, spite and pride.