Musnad Ahmad 468:0

Narrated to us by Yahya ibn Sa’id, from Ibn ‘Ajlan, who said: Narrated to me my father, from Abu Namlah al-Ansari, that the Messenger of Allah (ﷺ) said: "Whoever has wealth that reaches the amount upon which Zakat is due, let him pay its Zakat. And whoever has wealth that reaches the amount upon which Hajj is due, let him perform Hajj. And whoever has wealth that reaches the amount upon which he is asked, let him give." Abu Namlah said: "I asked him: 'What is the amount upon which he is asked?'" He (the Prophet) said: "Fifty dirhams, or their equivalent in gold."