"Two Scotsmen" joke

Two Scotsmen had been pals since childhood and had shared everything over the years.
One day, Angus won a rare bottle of Scotch in a door prize.
Immediately, Jock says “Open it up and we’ll have a dram. ”
“Naw, ah’m goin’ tae save it for a special occasion. ”
Birthdays came and went, his anniversaries came and went, but Jock could never get Angus to open the bottle.
Finally Angus had a heart attack, and was laying on his deathbed.
He motioned for his old friend to come closer.
“Jock, remember that rare bottle of Scotch I won? ”
“Aye, ah certainly do, Angus! ”
“Weell, ah like ye tae do me a favor Jock, my dear friend. ”
“Aye, anything ye ask Angus. ”
“When ah’m dead, wid ye take that bottle an’ open it up–”
“Aye, Angus, then what? ”
“Wid ye pour it over ma grave? ”
“Pour it over yer grave? My god Angus. It’s 40 year old Scotch! But I’ll do it for ye. ”
“Oh, ye’re a real pal Jock, and ah’ll appreciate that. ”
Jock says,
“There’s just one thing Angus, wid ye mind if ah filter it through my kidneys first? ”