Hilal al-Wazzan said: I heard Ibn Abi Layla say: A man came to Sayyiduna Umar (may Allah be pleased with him) and said: O Commander of the Believers! Give me a mount. He said: By Allah! I will not give you a mount. He said: You will certainly give me a mount. Sayyiduna Umar (may Allah be pleased with him) said: I will not give you a mount. He said again: You will certainly give me a mount; I am a traveller, and my mount is exhausted. Sayyiduna Umar (may Allah be pleased with him) said: I will not give you a mount, by Allah! Until he had sworn nearly twenty oaths.
A man from the Ansar said to him: What is the matter between you and the Commander of the Believers? He said: I am a traveller, my mount is worn out, and he ought to give me a mount, but he says: By Allah! I will not give you a mount.
The narrator said: Sayyiduna Umar (may Allah be pleased with him) said: By Allah! I will certainly give you a mount; then, by Allah! I will certainly give you a mount. Then he gave him a mount. Then he said: "Whoever swears an oath about something and something else is better than it, let him give the expiation for the oath and do the better thing." Ali bin al-Madini (may Allah have mercy on him) said: This hadith is gharib (unusual); the expiation is only one.
(b) The Shaykh said: There is no such evidence in it; but Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) also said that in an oath of this kind the expiation is only once.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19979