Mujahid, Qatadah and others said:

{upon the edge} means, in doubt. Others said that it meant on the edge, such as on the edge or side of a mountain, i.e., (this person) enters Islam on the edge, and if he finds what he likes he will continue, otherwise he will leave. Al-Bukhari recorded that Ibn 'Abbas said:

"People would come to Al-Madinah (to declare their Islam) and if their wives gave birth to sons and their mares gave birth to foals, they would say, 'This is a good religion,' but if their wives and their mares did not give birth, they would say, 'This is a bad religion.'"

Al-'Awfi reported that Ibn 'Abbas said, "One of them would come to Al-Madinah, which was a land that was infected with a contagious disease. If he remained healthy there, and his mare foaled and his wife gave birth to a boy, he would be content, and would say, 'I have not experienced anything but good since I started to follow this religion.'

{but if a Fitnah strikes him}, Fitnah here means affliction, i.e., if the disease of Al-Madinah befalls him, and his wife gives birth to a babe girl and charity is delayed in coming to him, the Shaytan comes to him and says: 'By Allah, since you started to follow this religion of yours, you have experienced nothing but bad things,' and this is the Fitnah." This was also mentioned by Qatadah, Ad-Dahhak, Ibn Jurayj and others among the Salaf when explaining this Ayah. Mujahid said, concerning the Ayah:

{he turns back on his face.} "(This means), he becomes an apostate and a disbeliever."

means, he does not gain anything in this world. As for the Hereafter, he has disbelieved in Allah the Almighty, so he will be utterly doomed and humiliated. So Allah says:

{That is the evident loss.}, i.e., the greatest loss and the losing deal.

means, the idols, rivals, and false gods which he calls upon for help, support and provision - they can neither benefit him nor harm him.

means, he is more likely to harm him than benefit him in this world, and in the Hereafter he will most certainly cause him harm.

Mujahid said, "This means the idols. The meaning is: "How evil a friend is this one upon whom he calls instead of Allah as a helper and supporter."

{and certainly an evil 'Ashir!} means the one with whom one mixes and spends one's time.