The Messenger of Allah ﷺ said, "Allah has said to me, 'Spend, and I will spend on you.'"He also said, "Allah's hand is full. No expenditure diminishes it, pouring forth night and day."He said, "Have you considered all that He has spent since He created the heavens and the earth? It has not diminished what is in His hand. His Throne was upon the water, and in His hand is the balance, lowering and raising."
أن رسول الله ﷺ قال: إن الله قال لي: أنفق أنفق عليك. وقال: يد الله ملأى، لا تغيضها نفقة سحاء الليل والنهار. وقال: أرأيتم ما أنفق منذ خلق السماء والأرض؟ فإنه لم يغض ما في يده وكان عرشه على الماء، وبيده الميزان يخفض ويرفع.
Bukhari related it in the Tafsir (4684), and Muslim in the Zakat (993), both of them through Abu Zinad, from Aaraj, from Abu Hurairah, who mentioned it. The wording given is Bukhari's.