I once heard in a lecture that when Shimr (la) sat on the chest of Aba Abdillah (as), hazrat said to him:

"O Shimr, if you give me water I will intercede for you on the day of Judgment"

Is there any source for this quote (even weak) in our books? Because I couldn’t find it.
If not, what did Hazrat really say at that moment?

There is no such statement by the Imam and it goes against what we know of his dignity and strength. He was supplicating in those last moments