The scholar  Abdur Rahmaan ibn Nasir as Sa’dee rahimahullaah said about the statement of Allaah, the Most High:

<<And when some harm touches man, he calls upon his Lord repentantly.
Then when He bestows a blessing upon him from Himself, he forgets that which he was supplicating about beforehand and he sets up rivals along with Allaah.>>
(Soorah az Zumar (39) aayah 8)

He, the Most High, informs (us) of His generosity to His servant, and His fine treatment and goodness to him – and how little is the gratitude of His servant.

And that when harm touches him, by way of illness or poverty or falling into difficulty at sea or other than that (and) that he knows that none can save him in this situation except Allaah, then he calls upon Him beseeching (Him) and turning in repentance; and he seeks rescue from Him for the removal of that which has befallen him and he implores (Him) in that.

Then when He bestows a blessing – (meaning) Allaah

a blessing upon him from Himself – in that He takes away the harm and distress that he had

he forgets that which he was supplicating about beforehand –  meaning: he forgets that harm about which he had called upon Allaah; and he continues as if no harm had afflicted him and he persists upon his shirk.

(Tayseer ul Kareem ir Rahmaan of as Sa’dee rahimahullaah, translated by Nasser ibn Najam)

Explanation of Ayah 175-176 from Surat-ul-A’raaf

By Shaikh Abdur Rahman Ibn Nasir as Sa’di

Allaah said to His prophet (Peace be upon him),

< و اتل عليهم نبأ الذي آتيناهم آياتنا >

And inform them about the one who we gave our signs to.

i.e. we taught him the book of Allaah (Quraan), and so became learned.

< فانسلخ منها، فأتبعه الشيطان >

But he turned away from them and Satan followed him.

i.e. he physically turned away with knowledge of the book of Allaah. One who has knowledge of this (quraan) makes the person from the best and noblest  manners and purist of actions which take the person to the highest of stations, yet he abandons this and puts the book of Allaah behind him, renounces the manners which the Quraan orders and strips himself of it just as he removes his clothes.

So when he turns away from this Satan follows him, meaning, Satan overcomes him as he has now left the best of fortified fortresses and has now become from the lowest of the lowest and in turn he is led to sins,

< فكان من الغاوين >

and so became from those astray.

After he was once from those who were rightly guided and guided others. Because Allaah lowered him and left him to his own devices. Allaah says in this regard,

< و لو شئنا لرفعناه بها >

and had We willed we could have raised him because of it.

i.e. We could guide him to act upon it ( his knowledge ), and so would be elevated in this life and the next and be protected from his enemies.

< و لكنه >

But rather he…

did that which caused his misguidance when he..

< أخلد إلى الارض >

Clung to the earth…

i.e he clung to lowly desires and worldly possessions.

< و اتبع هواه >

And followed his desires…

i.e he stopped obeying his Lord.

< فمثله >

So his example…

i.e in regards to the extreme importance he places to this life and the attachment of his heart to it.

< كمثل الكلب إن تحمل عليه يلهث أو تتركه يلهث >

Is like that of a dog. If you chase him away he pants or if you leave him be he still pants.

i.e. He will not stop panting in every situation. Just like this one who is constantly seeking this worldly life with all his heart that he may lose something from the worldly possessions.

< ذلك مثل القوم الذين كذبوا بآياتنا >

That is the example of those who disregard our signs…

i.e. After Allaah had guided them but they never followed them, rather they disbelieved and rejected them due to Allaah disgracing them, following their desires and without guidance from Allaah.

< فاقصص القصص لعلهم يتفكرون >

So narrate the stories, perhaps they may reflect.

i.e. In putting forth for the people examples, lessons and signs. So if they reflect, they will know, and when they know they will act.

Translated by Abu Salmaan Talha ibn William