Islamic Ruling on Replying to Salaam by Message or WhatsApp

According to Islamic scholars if a person sends Salaam in written form then replying immediately is obligatory. Sending Salaam through WhatsApp is also considered the same as written Salaam. Therefore replying to a Salaam sent on WhatsApp must be done immediately. Imam Nawawi explains in this fatwa that if someone gives Salaam from behind a wall or sends Salaam through a letter or a messenger and the Salaam reaches the person then it is obligatory to reply to it immediately. This shows the Islamic ruling clearly that written or message based Salaam requires an immediate reply according to Islamic fiqh.