prayer: command not found

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 Debian possible default full paths are:

/usr/sbin/prayer - from package: prayer

You may install the required package with command apt-get install {package}

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