Innal lazeena attaqau--- This is said about those whose hearts are free of the thoughts of sin. When the heart is pure and clean, then automatically all other organs get into sound repair. Therefore, the tongue, the eyes, the ears and the limbs do not get associated with any wrong act.

Iza massahum taaef--- Taaef is a person who does tawaaf or circumambulates. Here it is meant Satan going round the heart in search of a hole to break in.

Min al Shaitan--- it is the mention of the retainers of Satan who go round the heart in search of an opening to barge in. But

Tazkkaru--- The owner of the heart, a momin, is busy in Remembrance of Allah and says, "Ya Allah- Astghfar Allah- Aaoozu billahi min al Shaitan ir rajeem-O Allah! Protect me from the harm that Satan can cause me!"

Hence,
Fa izahum mubseroon--- Their eyes instantaneously illuminate with the light of vision and they get warned of the thief in their environs.

Here I wish to point at the words Taaef min al Shaitan which connote that the one who takes rounds of the heart of a momin to find an entry is from the group of Satan.

Remember! If there is piety (Taqwa) for Allah in the heart, then it will be pure and clean. The bright light of piety will put the thief to shame and he escapes from there. Pity the heart that is devoid of piety and full of worldly desires. Such a person will fall into the clutches of Satan and meet a sad end.