Can You Pray in Your sleepwear?
Question

Do the clothes you wear to sleep become impure (so you are not allowed to pray in them)?
Praise be to Allah.Does sleeping in clothes make them impure?
The basic principle with regard to clothes is that they are pure , unless any impurity has gotten onto them, in which case they must be purified. 
Merely sleeping in clothes does not make them impure; rather they remain pure until it becomes certain that any impurity has gotten onto them . 
Shaykh Ibn ‘Uthaymin (may Allah have mercy on him) said: 
“The basic principle with regard to a person wearing clothes is that he (and they) are pure so long as he is not certain that any impurity has gotten onto his body or clothes. This basic principle is supported by the words of the Prophet (blessings and peace of Allah be upon him) when a man complained to him that he felt something during his prayer – referring to breaking wind. He said: “Do not stop (praying) unless you hear a sound or notice a smell.” If the individual is not certain about that, then the basic principle is that he remains pure. He may think it most likely that his clothes have become contaminated with impurity, but so long as he is not certain about it, the basic principle is that he remains pure.” (Majmu` Fatawa Ibn `Uthaymin, 11/107) 
Can you pray in sleepwear?
It is permissible to pray in clothes in which one has slept (sleepwear), so long as they are pure and cover the `Awrah, although it is better and more perfect to wear beautiful clothes that look good for prayer. That is in obedience to the command of Allah, may He be Exalted, in the verse (interpretation of the meaning): “O Children of Adam! Take your adornment (by wearing your clean clothes), while praying” [Al-A`raf 7:31] 
Shaykh Ibn `Uthaymin (may Allah have mercy on him) was asked about the ruling on praying in sleepwear and attending gatherings wearing them. 
He said: 
“There is nothing wrong with praying in sleepwear if they are pure, whether one comes to the mosque wearing them or not, unless those clothes will attract attention and criticism, and people will talk about him in their gatherings because of that. People should avoid anything that may be a cause of people backbiting about them.” (Majmu` Fatawa Ibn `Uthaymin, 12/362)
For more details, please see the following  answers: 46529 and 32993 .
And Allah knows best.