The wind(الهَيْف‏) has gone back to its customs ذَهَبَتْ هَيْفٌ لأَدْيَانِهَا‏.‏

The word "hayf" refers to a hot wind that blows from the direction of Yemen in the summer. Abu Ubaid said: The root of "hayf" is "simoom" (a type of wind). The phrase "to its customs" is the plural of "deen," meaning custom or habit. It is pluralized because "hayf" is a generic noun, and the preposition "li" (to) is used to indicate "to," meaning it has returned to its customs. Its custom is to dry and wither everything. This proverb is used when everyone goes their separate ways, and it is also said to be used for anyone who clings to their habits and does not deviate from them.
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This proverb, “Heif went back to her old ways,” is used in two senses:
For everyone to return to their usual ways and habits after a meeting or unexpected event.
For nature to prevail, and for a person to revert to their original habits and disposition.
Some of the closest English equivalents, according to the meaning, are:
If the meaning is returning to one's old habits and disposition:
“Old habits die hard.”
Meaning: Old habits die hard.
This is the most common and closest equivalent.
“A leopard cannot change its spots.”
Meaning: A leopard cannot change its spots.
Used to describe someone who returns to their old habits and disposition.
“He has gone back to his old ways.”
Meaning: He has returned to his old habits.
If the meaning is that people dispersed, each going their separate ways:
“Everyone went their separate ways.”
Meaning: Each went their own way.
“Each to his own.”
Meaning: Each has their own business and way of doing things.
“Business as usual.” That is, everything returned to how it was before.
The closest equivalent to the Arabic proverb is:
“Old habits die hard.”
“Old habits don't disappear easily.”
If the intended meaning is the separation of people after their gathering, the closest equivalent is:
“Everyone went their separate ways.”
“Each went his own way.”
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الهَيْف‏:‏ الريح الحارة تَهُبُّ من ناحية اليمن في الصيف، قال أبو عبيد‏:‏ وأصل الهَيْفِ السموم، وقوله ‏"‏لأديانها‏"‏ جمع دِين، وهو العادة، أي لعاداتها، وإنما جمع الأديان لأن الهيف اسم جنس، وجاء باللام على معنى إلى، أي رجعت إلى عاداتها، وعادتُهَا أن تجفف كل شيء وتيبسه‏.‏ يضرب مثلا عند تفرق كل إنسان لشأنه، ويقال‏:‏ يُضرب لكل مَنْ لَزِمَ عادته ولم يفارقها‏.‏