Sanhedrin (65b) Raba said: If the righteous desired it, they could [by living a life of absolute purity] be creators, for it is written, But your iniquities have distinguished between etc. Rabbah created a man, and sent him to R. Zera. R. Zera spoke to him, but received no answer. Thereupon he said unto him: Thou art a creature of the magicians. Return to thy dust.R. Hanina and R. Oshaia spent every Sabbath eve in studying the ‘Book of Creation’, by means of which they created a third-grown calf and ate it.
Yad Ramah (65b) Raba said, If the righteous desired it they could create a world. These are the Tsadikim who if they wanted to be freed from all iniquity they could create a world by their merit Because G-d fulfills their decrees. It is said that Your sins distinguish between you and your God, So if they didn’t sin There would be no difference between the servant and his Master, but the Master fulfills his decrees as He does His own.