Taqiyya is tactical deceit for the purposes of spreading islam, it is one of the the six forms of islamic deceit (others are Kitman, Tawriya, Taysir, Darura and Muruna).
Taqiyya (a.k.a. taqiya or taqiyah or taqiyyah) comes from Koran 16:106 and 3:28, Bukhari 5,59,369 and 4,52,268, Reliance of the Traveler, Para r8.2.
Reliance of the Traveler says: “When it is possible to achieve an aim by lying but not by telling the truth, it is permissible to lie if attaining the goal is permissible, and lying is obligatory if the goal is obligatory.”
Note: the highest goal of islam is making sharia the law of the land.
Also the koran commands: “Let believers not make friends with infidels in preference to the faithful”.
So, because islam permits lying to advance islam, ANY MUSLIM can actually put his hand on the koran and swear an oath, promise something, or sign an agreement (remember Turkey and Iran?) to A-N-Y-T-H-I-N-G while lying about it and it will be NO PROBLEM AT ALL. As long as it advances islam it’s all fine by Allah.
Taqiyya is the very first thing you need to understand about islam! In this video David Wood explains the islamic doctrine of taqiyya perfectly.