Those 3 letters و - ب - ت are called "حروف القسم" (swearing letters), they all can be used to give the same meaning but there are differences between them: 1) ب : can be used with the "swearing verb" "فعل القسم" , and can be used with all nouns and pronouns, examples: بالله سأسافر = with noun "ويحلفون بالله إنهم لمنكم" \ "لا أقسم بيوم القيامة" = with verb and noun يا رب أقسمت بك = with verb and pronoun "ك" 2) و : can be used with all nouns, but NOT pronouns, and can NOT have a verb, examples: والله سأسافر \ والنجم إذا هوى \ والسماء والطارق 3) ت : can ONLY be used with the name "ALLAH", and can NOT have a verb, example: "قالوا تالله إنك لفي ضلالك القديم" Note: because the "ب" is the only form that can have a verb, it's the only form that can be used for requests, as in swearing that someone else should do something, as in "بالله سافر" (by Allah, travel) because it's originally "أقسمت عليك بالله" (I swear by Allah on you "to do this") , and it's shortened to "بالله" or "بالله عليك" , other forms cannot be used in the same manner.

Salam Mudasser, Regarding والله، بالله، تالله, as you already know they are used to swear by Allah: and they all give the same meaning: "I swear by Allah", yet والله is widely used, and after that comes بالله, and the least used between them is تالله. I don't remember anyone who used to swear by the 3 of them except my late father, and even then, they used to sound weird to my ears to be honest, because I only read تالله in Quraán, but except for my late father in real life, I've never heard تالله being used. Those are 2 examples I hear sometimes where you can use والله، بالله: والله: والله سأفعل ذلك غدًا: I swear by Allah that I'll do that tomorrow. بالله: أقسم بالله عليك أن تقول الصدق: I swear by Allah that you should tell the truth. Sometimes, in daily life بالله/ والله is used much even though we shouldn't swear by Allah's name in every little matter! So be aware to use them when something really matters. As Amira have mentioned, sometimes we reply a simple question with والله لا أعرف! There's honestly no need to mention Allah's name in the case, because there's no need to swear in the first place. I hope this helps you understand how to use them. Good luck.

From what I heard in real life: والله - the most one I've heard, usually people use it when they want to prove something, even if it's not very important. For example: من أين اشتريت هذا الثوب؟- - والله لا أعرف، لقد أتاني هدية تالله - has the the same meaning as "والله", but I've never heard it in conversational Arabic. From what I found in the Internet "ت" is used only before swearing with the word God "الله". But "و" can be used when swearing by other things (و الليل، و الشمس). بالله - I heard it used with the word "عليك" and it means like "I swear by you". e.g. - أخبرني، ماذا حصل؟ - لا أريد - بالله عليك، أخبرني

I do not know English so I write with the aid of an interpreter , these words are the greatest curse of Islam . and God is not a specific word and Allah is certain why some sounds like a One God .

as you know Arabs before Islam were famous for trying to show their eloquence, so they invent different ways to describe things, and swearing is one of those things .