Musannaf Ibn Abi Shaybah

Hazrat Salim bin Abdullah (may Allah be pleased with him) disliked that anyone should say to another: I will compete with you on the condition that you will make me lie down (i.e., give me a reward, etc.).

Hasan (may Allah have mercy on him) disliked that it be said: "I will compete on the condition that you let me advance."

Ibrahim (may Allah have mercy on him) said that the noble Companions j disliked that a person would say to another: "I will compete with you on the condition that you will let me go ahead, then if I surpass you, the prize will be mine, otherwise it will be yours." He said, this is gambling.