This Surah has been separated from the one that preceded it in the primary Mushaf (the original copy of `Uthman) .
They (the Companions) wrote "In the Name of Allah, the Most Gracious, the Most Merciful" on the line (i.e., the space) between these two Surahs. They did this even though this Surah is directly related to the one which precedes it, as Muhammad bin Ishaq and `Abdur-Rahman bin Zayd bin Aslam have both clarified. This is because the meaning of both of them is,
"We have prevented the Elephant from entering Makkah and We have destroyed its people in order to gather (Ilaf) the Quraysh, which means to unite them and bring them together safely in their city."
It has also been said that the meaning of this (Ilaf) is what they would gather during their journey in the winter to Yemen and in the summer to Ash-Sham through trade and other than that. Then they would return to their city in safety during their journeys due to the respect that the people had for them because they were the residents of Allah's sanctuary. Therefore, whoever knew them would honor them. Even those who came to them and traveled with them, would be safe because of them. This was their situation during their journeys and travels during their winter and summer. In reference to their living in the city, then it is as Allah said,
أَوَلَمْ يَرَوْاْ أَنَّا جَعَلْنَا حَرَماً ءامِناً وَيُتَخَطَّفُ النَّاسُ مِنْ حَوْلِهِمْ
Have they not seen that We have made it a secure sanctuary, while men are being snatched away from all around them. (29;67).
Thus, Allah says,
لاِإِيلَإفِ قُرَيْشٍ
إِيلَـفِهِمْ
For the Ilaf of the Quraysh. Their Ilaf,
This is a subject that has been transferred from the first sentence in order to give it more explanation.
Thus, Allah says,
إِيلَفِهِمْ رِحْلَةَ الشِّتَاء وَالصَّيْفِ