Does the clipping of nails nullify ablution?
No, it does not, and it is preferable to wash the hands afterwards.
Who should pay the Zakah (obligatory charity) from the orphan`s money?
His/her guardian, and if the latter fails to do so, then the orphan himself/herself is obliged to pay the Zakah once he/she reaches puberty, and is capable of handling his/her own affairs. And Allah Knows Best.
What is the ruling on eating and drinking at night after making the intention? Is it necessary to renew the intention?
Eating and drinking at night, even after making the intention (for the next day), does not affect the fast, and it is not necessary to renew the intention after eating and drinking.
What is the ruling of Islamic Law regarding one who slaughters a ewe and it turns out to have been pregnant, and is it permissible to slaughter the ewe if one knows it is pregnant?
Praise be to Allah, and peace and blessings upon our master, the Messenger of Allah.
If a person slaughters a ewe and it turns out to have been pregnant, the fetus becomes lawful (ḥalāl) by virtue of its mother's slaughter (tabaʿan li-ummihā).
It is stated in Mughnī al-Muḥtāj (Vol.6/P.158): "A fetus found dead [after the mother's slaughter], or found alive but in a state resembling that of a slaughtered animal [i.e., dying shortly after], becomes lawful — whether or not it had grown fur — provided it is found in the womb of a mother that was lawfully slaughtered, whether her slaughter was by cutting the throat, or by an arrow or hunting dog sent after her. This is based on the ḥadīth: 'The slaughtering of the fetus is [effected by] the slaughtering of its mother' [narrated by al-Tirmidhī, who graded it ḥasan, and by Ibn Ḥibbān, who graded it ṣaḥīḥ] — meaning that the slaughter which rendered the mother lawful renders the fetus lawful as well, by virtue of following her; and because the fetus is one of her constituent parts, and her slaughter renders lawful all of her parts."
This ruling differs, however, from the case of one who knows from the outset that the ewe is pregnant [and intends to sacrifice her specifically as the udḥiyah while pregnant] — in which case, according to the Shāfi'ī school, she does not fulfill the requirement of a valid sacrifice.
It is stated in Ḥāshiyat al-Bujayrimī 'alā al-Khaṭīb (Vol.4/P.335): "A pregnant animal does not fulfill the requirement [of a valid sacrifice], and this is the authoritative position (al-mu'tamad), because pregnancy diminishes the quality of the meat. As for why such an animal is nevertheless counted as complete [i.e., fully valid] in matters of zakāh, that is because the intent there is reproduction (nasl), not the quality of the meat.". And Allah, the Most High, knows best.
