He is merely throwing the idea forward for discussion, it is not cast in stone.

他只是抛出个想法供讨论，不是固定不变的。

《柯林斯英汉双解大词典》

Although Ben saw the girl cheating he did not want to cast the first stone.

本虽然看见那女孩作弊，但不愿带头揭发她。

youdao

They have cut off my life in the dungeon, and cast a stone upon me.

他们使我的命在牢狱中断绝，并将一块石头抛在我身上。

youdao

The numbers may be either too high or too low depending on how the economy is going at any given time, and I am really doubtful anyone has the ability to cast in stone the proper standards.

FORBES: Intelligent Investing Briefing Book

Whether it's an iPhone at work or a copy of Sports Illustrated at home, let he who is without a magazine in his bathroom cast the first stone.

CNN: Apparently This Matters: iPotty

You can cast the first stone.

NPR: Aretha Franklin's Globe-Nominated Performance