Al-Ankabut (The Spider): (67) Or have they not seen...

The apparent meaning is clear. The subtle point lies in how this verse connects to the preceding one.

We say: A person at sea is in the utmost state of fear, whereas in his home, he is in the utmost state of safety, especially if his home is in a fortified city.

When Allah mentioned the state of the polytheists during intense fear, and how they turned back to Him in that situation, He then reminds them of their state during great security—which is their being in Mecca. It is their city, their land, and the place of their dwelling and birth. It is fortified by the fortress of God, as everyone around it refrains from fighting those who reside within it. Dwelling there wards off evils from their souls and restrains them.

The meaning is: When you were in the greatest fear, you called upon God, but when you attained the greatest security, you disbelieved in God. This is contradictory, because your supplication at that time was sincere, stemming from your conviction that blessings come only from God. How then can you disbelieve in this great blessing that you attained, having acknowledged that it can only come from God? And how can you trust in the idols for security when you were certain during the time of fear that they offer no safety?