Praise be to Allaah.
The verse means what it appears to mean, which is that Allah, may He be glorified and exalted, controls the affairs of His slaves. So He may guide one person and open his heart to faith and guide him to Islam, or He may place some reluctance in his heart and make him uneasy about the religion of Allah, which prevents him from coming to Islam, so He comes in between a person and his heart, as it says in the verse [interpretation of the meaning]: “And whomsoever Allaah wills to guide, He opens his breast to Islam; and whomsoever He wills to send astray, He makes his breast closed and constricted, as if he is climbing up to the sky” [al-An ‘aam 6:125].
So Allah is the One Who controls the affairs of His slaves however He wills. So He opens the heart of one person to faith and guidance, whilst another person is not helped and guided to that. End quote.
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him)