Each clashing player reveals the top card of their library at the same time. Then those players decide in APNAP order (see rule 101.4) where to put those cards, then those cards move at the same time.
July 3, 2020 · Core Set 2021
rule 701.30c not present in this release
May 3, 2019 · War of the Spark
If a permanent’s ability instructs a player to “monstrosity X,” other abilities of that permanent may also refer to X. The value of X in those abilities is equal to the value of X as that permanent became monstrous.
January 25, 2019 · Ravnica Allegiance
If a permanent's ability instructs a player to "monstrosity X," other abilities of that permanent may also refer to X. The value of X in those abilities is equal to the value of X as that permanent became monstrous.
April 27, 2018 · Dominaria
If a permanent’s ability instructs a player to “monstrosity X,” other abilities of that permanent may also refer to X. The value of X in those abilities is equal to the value of X as that permanent became monstrous.
September 30, 2016 · Kaladesh
If the text of a spell or ability refers to “voting,” it refers only to an actual vote, not to any spell or ability that involves the players making choices or decisions without using the word “vote.”