Al-Kāfi
Hadith 2481عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ سَهْلِ بْنِ زِيَادٍ رَفَعَهُ قَالَ قَالَ أَبُو عَبْدِ اللَّهِ ( عليه السلام ) مَا أَتَى مِنْ ثَلَاثِينَ فَرْسَخاً فَبِالْهِدَايَةِ وَ مَا كَانَ أَكْثَرَ مِنْ ذَلِكَ فَبِالْأُكُلِ .
2. A number of our people have narrated from Sahl ibn Ziyad in a marfu‘ manner has said the following: “Abu ‘Abd Allah (a.s.), has said, ‘That (bird) which comes back from a distance of thirty farsakh is because of guidance and from a distance of more than this is because of food.’”