Cutting the nails is Mandoob due to what was related from ‘Aa’ishah (ra) when he said: The Messenger of Allah صلى الله عليه وسلم said: “There are ten from the (acts of) Fitrah:…and cutting the nails…” recorded by Muslim and others and by what Abu Hurairah (ra) related that the Messenger of Allah صلى الله عليه وسلم said: “The Fitrah are five: …and trimming the nails” recorded by Muslim and others, and these two Hadeeth have been previously quoted in full.
Forty days has been set as the furthest limit for us to cut or trim the nails so if he was to cut them in less time than that then it would be nearer to meeting the requirement of cleanliness because if the nails grow long dirt builds up under them and food and drink could mix with this dirt.
Abu ayoob Al-‘Atki said: The Messenger of Allah صلى الله عليه وسلم said: “One of you asks about the news from the sky whilst he leaves his finger nails like the nails (claws) of birds in which filth, dirt and grime gathers” as recorded by Ahmad and At-Tabaraani.
Al-Haithami said: “Its transmitters are Saheeh except Abu Waasil and he is trustworthy.”
In addition if the nails were to grow long it could cause harm or inflict wounds and so the command came to cut them. Sawaada Bin Ar-Rabee’ said: “I approached the Nabi صلى الله عليه وسلم and asked him: He commanded a Dawd (type of camel between two and nine) and then said: When you have returned to your house then command them to feed the camel offspring well and to cut their nails and don’t wound with them (the nails) the udders when they are being milked” as recorded by Ahmad. These two Hadeeth explain the purpose of cutting the nails and indicates in addition that the cutting is Sunnah as well as the cutting of the nails being from the Fitrah. It is Sunnah to begin the cutting with the fingers of the right hand and then the left followed by the toe nails of the right foot and then the left, and this is due to the Hadeeth about starting with the right first mentioned previously (above).
And here it is necessary to bring the attention to an important point specifically related to women and the nail polish they apply. This polish applies a thick (solid) layer which prevents the water when washing to reach the nails which would lead to the corruption of the Wudoo or Ghusl and women should take note to leave the Zeenah (act of beautification) and it is possible for them to use Hennaa instead unless they were to remove this polish upon making every Wudoo’ and Ghusl which would be a hardship upon them. And to know more about this then please revise the chapter: (Al-Wudoo’) in the section: (The description of the Wudoo’).