Assalamu 'alaykum wa rahmatullaahi wa barakatuh.
This is a really good refresher on Tawheed. It is a series of eight short sectional lectures.
Here is the first one...
What is Tawheed? and what's so important about it? This is the topic Abu Khadeejah Abdul-Wahid covers in this top-notch lecture, so please listen to it wa barakAllahu feekum.
The principle of Tawheed is the fundamental principle of Islam on which all other principles, rules and pillars are based. The aspect of Tawheed emanates from the Shahada "There is no deity worthy of worship except Allah and Muhammad is His servant and Messenger". It is this declaration that forms the dividing line between Iman (belief) and Kufr (disbelief).
Wasalamu 'alaykum wa rahmatullaahi wa barakatuh!
Praise be to Allah, and may His Blessings and Peace be upon Muhammad, his family and companions.
nuh ibn zbigniew