COPY & PASTE the code in a .cfg file you must create in the cstrike folder found in your installation directory.
I made mine bhop.cfg
Paste the code inside then open the game.
Open the console and write "exec bhop.cfg" (without the "")
then write (no < >)

alias +jump_2 "alias _special j_bhop; j_start; +duck"
alias -jump_2 "alias _special j_stop; -duck"
alias j_bhop "+jump;wait;-jump;wait;j_start"
alias j_start "special"
alias j_stop " "

bind "space" "+jump_2"