he: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/var/spool/hylafax/bin/dict/he - from package: hylafax+

You may install the required package with command yum install {package}
Error in other languages:
he: bevel nie gevind nie
he: comandă negăsită
he: comando não encontrado
he: commande introuvable
he: command not found
he: käsku ei ole
he: không tìm thấy lệnh
he: komanda nerasta
he: Kommando nicht gefunden.
he: kommandot finns inte
he: komut yok
he: nie znaleziono polecenia
he: níor aimsíodh an t-ordú
he: no se encontró la orden
he: no s'ha trobat l'ordre
he: opdracht niet gevonden
he: parancs nem található
he: perintah tidak ditemukan
he: príkaz nenájdený
he: příkaz nenalezen
he: команда не найдена
he: командата не е открита
he: 命令找不到
he: コマンドが見つかりません