Nas threw a jab at 50 on his "Untitled" album saying "My assignment since he said retirement," referring to 50 saying he would retire if Kanye West outsold him last year, continuing "hiding behind 8 Mile and The Chronic, Gets rich, but dies rhymin, this is high science."
In the new issue of XXL Magazine, 50 Cent spoke on the shot, kind of. When asked about the rhyme on the song "Queens Get The Money," the G-Unit general first praised the rapper saying "Man, Nas is cold as ice. Nas is the block of ice that sunk the Titanic." Being 50, he did continue on by saying "I think he's at one of those points to where his career's finished, to be honest. He's had some great moments and made good music in the past, but he no longer has the interest of the general public or myself."
Source: http://www.rapbasement.com/50-cent/1202 ... ished.html