"And he was a successful man" (Genesis 39:2). He would gird his loins, and when his master said to him, "Mix me a cup of hot water," he would mix it. "Give me cold water," and he would give it to him from that same vessel. His master would say to him, "Give me wine," and he would give it to him. "Give me a threefold mixture" (wine mixed with two parts water), and he would give it to him. And it would sweeten of its own accord. Therefore it is said, "And he was a successful man."
Joseph's Miraculous Service in Potiphar's House
Midrash Tanchuma Buber, Vayeshev 16:5
ויהי איש מצליח. היה חוגר מתניו ואדונו אומר לו מזוג לי כוס חמין והוא מוזג, תן לי צונן והוא נותן לו מאותו מכלי, אדונו אומר לו תן לי יין והוא נותן לו, תן לי משולש הוא נותן לו, ומאליו היה מתמתק, לכך נאמר ויהי איש מצליח.