Allah, glorious is His praise, said concerning the compensation for game: "An offering brought to the Ka'bah, or an expiation: the feeding of needy people, or the equivalent of that in fasting." [Surah al-Ma'idah: 95]
Imam Ata (may Allah have mercy on him) said: "(He may choose) whichever of them he wishes; and wherever the words 'or, or' occur in the Qur'an, the person has the choice to pick whichever of them he wishes."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / Q9894
Amr bin Dinar (may Allah have mercy on him), concerning the saying of Allah Almighty: "Then a ransom of fasting or charity or sacrifice" [Surah al-Baqarah: 196], says: He may give whichever he wishes.
Amr bin Dinar (may Allah have mercy on him) says: In everything in the Qur'an (stated with) 'or, or', he may give whichever he likes.
Ibn Jurayj (may Allah have mercy on him) said: Except this saying of Allah Almighty: "The recompense of those who wage war against Allah and His Messenger" [Surah al-Ma'idah: 33]; in this there is no choice.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9894
Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "If you wish, offer a sacrifice; if you wish, fast three days; and if you wish, feed six needy people three sa' (of food)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9895