It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever enters a horse between two horses while he is certain of its winning, that is gambling; and whoever adds a third horse between two horses while he also fears its losing, that is not gambling."
Only Sufyan bin Husayn and Sa'id bin Bashir narrated it from al-Zuhri.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19771