Umar bin Khattab reported,

He gave a horse to be used in the cause of Allah. Later he saw it, or one of its offspring, being put up for sale, and he wished to buy it. So he asked the Prophet ﷺ about it.The Prophet ﷺ said, "Leave it, so that it may come back to you complete," or, "so that you may meet it complete." He said this twice, forbidding him and saying, "Do not buy it, and do not take back what you have given in charity."

Ahmad 166

Sahih

حدثنا سفيان عن زيد بن أسلم

عن أبيه أن عمر

حمل على فرس في سبيل الله فرآها أو بعض نتاجها يباع فأراد شراءه فسأل النبي ﷺ عنه فقال اتركها توافك أو تلقها جميعا وقال مرتين فنهاه وقال لا تشتره ولا تعد في صدقتك

أحمد 166صحيح
Contents
Reference
Commentary
Ayat
Collection
Musnad Ahmad
Book
Umar bin Khattab
Numbering
Darussalam 166
Ahmad 166