Praise be to Allaah.
The usual greeting is “Assalaamu
‘alaykum wa rahmat-Allaahi wa barakaatuhu (Peace be upon
you, and the Mercy of Allaah and His Blessings), because Allaah says
(interpretation of the meaning):
one another with a greeting from Allaah (i.e. say: As-Salaamu
‘Alaykum — peace be on you), blessed and good”
The ahaadeeth explain this greeting
But bowing is not permitted, unless
the person being greeted is old and is unable to stand up, or is one
of your parents and you do not want to make him or her stand up to shake
your hand or embrace you. So if you bow and kiss his head or forehead
out of respect for the rights that he has over you, then this is not
the kind of bowing that constitutes an act of worship. Undoubtedly bowing
is an act of worship towards Allaah, as in rukoo’ (the bowing in prayer),
so if that is done without shaking hands or kissing, it is an act of
veneration towards that person and is therefore shirk.
Shaykh ‘Abd-Allaah ibn Jibreen.