The first offspring of a camel. --أول الصيد فرع

 The first offspring, the first calf born to a she-camel, was sacrificed to their gods as a blessing. A man would say, "When my camels reach such a number, I will sacrifice the first offspring." When they intended to sacrifice it, they would adorn and dress it. Thus, Aws said, describing a severe cold spell: "The general cold of the people resembled a young camel, adorned and dressed."

Abu Umar said: This proverb is used when one sees the first good fortune in crops, livestock, or any other benefit. It is also narrated, "The first offspring of a camel and its first sacrifice," because they would send the first thing they caught as a good omen. Another narration states, "The first offspring of a camel," meaning the first thing whose blood was shed. The phrase "The first offspring of a camel" is used to describe someone from whom no good had been seen before this action.

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The closest English equivalents, depending on the context, are:

A good beginning makes a good ending.

Well begun is half done.

This is one of the most well-known proverbs.

The first fruits.

This refers to the first fruits or the first good things, and it is very close to the origin of the Arabic proverb.

This is a promising start.

Every journey begins with a single step.

If the intention is that the first success is the beginning of what follows.

However, if it is used in the sense mentioned at the end of the explanation—that is, the first good thing seen from someone—the closest expression is:

That’s the first good thing we’ve seen from him.

Or:

A promising first sign.

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الفرع، أول ولد تنتجه الناقة، كانوا يذبحونه لآلهتهم يتبركون بذلك وكان الرجل يقول: إذا تمت إبلي كذا نحرت أول نتيج منها، وكانوا إذا أرادوا نحره زينوه وألبسوه. ولذلك قال أوس يذكر أزمة في شدة البرد:

شبه الهيدب العام من الأقوام سقبا مجللاً فرعا

قال أبو عمر: ويضرب عند أول ما يرى من خير في زرع أو ضرع وفي جميع المنافع. ويروى، أول الصيد فرع ونصاب؛ وذلك أنهم يرسلون أول شيء يصيدونه يتيمنون به. ويروى، أول صيد فرعه أي أراق دمه، وأول رفع على تقدير هو أو هذا أول صيد فرعه. يضرب لمن لم ير منه خير قبل فعلته هذه.