What is the ruling on entering the state of ihram with a single lower garment for 'Umrah?
Machine translationRead the Arabic original
The questioner : There are some people in ihram who enter the state with only a single lower garment, not completing their ihram attire. Is this forbidden, or does it invalidate the 'Umrah? And what is the matter with that? I think he is saying that he wears nothing but a calculation.
The Shaykh : That is, some Muslims say that if the lower garment is exposed regarding his 'awrah, then if the lower garment is exposed to his 'awrah, then his ritual is valid. However, if the lower garment does not cover his 'awrah, then his ritual is not valid, because one of the conditions of tawaf is covering, as it came in the authentic hadith: "No one shall perform tawaf while naked." So if the lower garment covers the 'awrah, then his ritual is valid with that, but it is better to enter ihram with a lower garment and an upper garment.
The Shaykh : That is, some Muslims say that if the lower garment is exposed regarding his 'awrah, then if the lower garment is exposed to his 'awrah, then his ritual is valid. However, if the lower garment does not cover his 'awrah, then his ritual is not valid, because one of the conditions of tawaf is covering, as it came in the authentic hadith: "No one shall perform tawaf while naked." So if the lower garment covers the 'awrah, then his ritual is valid with that, but it is better to enter ihram with a lower garment and an upper garment.
Source
دروس وفتاوى المسجد الحرام لعام 1402هـ - 3 — binothaimeen.net (6:21)
The Arabic text is a machine transcription of the audio recording.