It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Whoever bears witness that I am the Messenger of Allah, let him not attend the prayer while holding back his urine until he has relieved himself."
"And whoever bears witness that I am the Messenger of Allah, if he leads a people in prayer, let him not single himself out in the supplication."
"And whoever bears witness that I am the Messenger of Allah, let him not enter upon the people of a house until he has asked permission and given the greeting of peace; and once he has looked inside the house, it is as though he has already entered."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7474