The word(s) "unable" appears 14 time(s) in 13 verse(s) in Quran in Abdullah Yusuf Ali translation.

(11) And if any has not (the wherewithal), he should fast for two months consecutively before they touch each other. But if any is unable to do so, he should feed sixty indigent ones, this, that ye may show your faith in Allah and His Messenger. Those are limits (set by) Allah. For those who reject (Him), there is a grievous Penalty.

(12) When thou lookest at them, their exteriors please thee; and when they speak, thou listenest to their words. They are as (worthless as hollow) pieces of timber propped up, (unable to stand on their own). They think that every cry is against them. They are the enemies; so beware of them. The curse of Allah be on them! How are they deluded (away from the Truth)!

(13) Thy Lord doth know that thou standest forth (to prayer) nigh two-thirds of the night, or half the night, or a third of the night, and so doth a party of those with thee. But Allah doth appoint night and day in due measure He knoweth that ye are unable to keep count thereof. So He hath turned to you (in mercy): read ye, therefore, of the Qur'an as much as may be easy for you. He knoweth that there may be (some) among you in ill-health; others travelling through the land, seeking of Allah's bounty; yet others fighting in Allah's Cause, read ye, therefore, as much of the Qur'an as may be easy (for you); and establish regular Prayer and give regular Charity; and loan to Allah a Beautiful Loan. And whatever good ye send forth for your souls ye shall find it in Allah's Presence,- yea, better and greater, in Reward and seek ye the Grace of Allah: for Allah is Oft-Forgiving, Most Merciful.