# in his own generation

"during his lifetime"

# served the purpose of God

"did what God wanted him to do" or "did what pleased God"

# he fell asleep

"he died" 

# was laid with his fathers

"was buried with his ancestors who had died"

# his body experienced decay

The phrase "his body experienced decay" is a less direct way of saying "his body decayed" or "his body rotted."