scl_source: 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 CentOS possible default full paths are:

/usr/bin/scl_source - from package: scl-utils

You may install the required package with command yum install {package}

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