Musnad Ahmad 595:13

Yunus ibn Muhammad narrated to us, Hammad ibn Zayd narrated to us, Mujalid narrated to us, from Qays ibn Abi Hazim, from al-Mustawrid ibn Shaddad, who said: The Messenger of Allah (ﷺ) said: "By the One in Whose hand is my soul, the world in comparison to the Hereafter is nothing but like a man who puts his finger into the sea, then withdraws it." He said: I was with the riders with the Messenger of Allah (ﷺ), and he passed by a dead lamb discarded on a dunghill. He said: "Do you see this? Is it insignificant to its owners?" They said: Because of its insignificance, they threw it here. He said: "By the One in Whose hand is my soul, the world is more insignificant to Allah than this is to its owners."