Praise be to Allah.
Al-Bukhaari (3292) and Muslim (2691) narrated from Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever says, ‘Laa ilaaha ill-Allaah wahdahu laa shareeka lah, lahu’l-mulk wa lahu’l-hamd wa huwa ‘ala kulli shay’in qadeer (there is no god worthy of worship except Allah alone, with no partner or associate. His is the Dominion and to Him be praise, and He is able to do all things)’ one hundred times in a day, will have (a reward) equivalent to freeing ten slaves, one hundred hasanaat (good deeds) will be recorded for him and one hundred sayyi’aat (bad deeds) will be erased from him, and he will be protected from the Shaytaan for that day until evening comes. No one can do anything better than what he has done except one who does more than that.”
There is no stipulation in the hadith that the dhikr mentioned should be repeated one hundred times consecutively in order to attain this virtue. What appears to be the case is that the matter is broad in scope, and that the criterion for attaining this reward is that it should be done all on the same day, not that it should be done consecutively.
An-Nawawi (may Allah have mercy on him) said:
The general meaning of the hadith indicates that the reward mentioned may be attained by the one who repeats this dhikr one hundred times in a day, whether he repeats it consecutively or at different times in several sessions, or he recites some of it at the beginning of the day and some at the end of the day. But the best is to recite it consecutively at the beginning of the day, so that it will be a protection for him throughout his day." (Sharh an-Nawawi ‘ala Muslim 17/17).
See also the answer to question no. 148699 .
There are hadiths from the Prophet (blessings and peace of Allah be upon him) which encourage and urge Muslims to free slaves, one of which is that which was narrated by al-Bukhaari (6715) and Muslim (1509) from Abu Hurayrah (may Allah be pleased with him), according to which the Prophet (blessings and peace of Allah be upon him) said: “Whoever frees a Muslim slave, Allah will ransom each of his limbs from the Fire for each of (the slave’s) limbs, even his private part for (the slave’s) private part.”
Ahmad (15417) narrated from Sahl ibn Hunayf, from the Prophet (blessings and peace of Allah be upon him) that whoever helps a mukaatab [a slave who has a contract of manumission with his master] to buy his freedom, Allah will shade him with His shade on the Day when there will be no shade except His shade.
There is no contradiction between the two hadiths at all, such that we might seek to reconcile between them. Rather the hadith which speaks of the virtue of this dhikr says that for the one who says “Laa ilaaha ill-Allaah wahdahu laa shareeka lah, lahu’l-mulk wa lahu’l-hamd wa huwa ‘ala kulli shay’in qadeer” one hundred times in a day there is the hope of reward, virtue and ransom from the Fire, just as there is the same hope for the one who liberates a Muslim slave from enslavement. This was stated clearly by al-Qaadi ‘Iyaad (may Allah have mercy on him). See: Sharh an-Nawawi ‘ala Muslim (17/18).
There is nothing in the hadith itself to explain what is hoped for the one who ransoms a Muslim slave.
Rather that is mentioned in the other hadith, which states that for each limb of the liberated slave, Allah will ransom from the Fire one limb of the body of the one who ransomed him. The grace of Allah is vast and His generosity is immense.
Ibn Rajab said:
The one who understands the true meaning of Tawheed will be motivated to free slaves, and freeing slaves will be rewarded with ransom from the Fire, as it is proven in as-Saheehayn that the one who says this dhikr one hundred times will have (a reward) equivalent to freeing ten slaves.
It is also proven that the one who says this dhikr ten times will be like the one who manumitted four of the descendants of Ismaa‘eel.
In Sunan Abi Dawood and elsewhere it is narrated from Anas that the Prophet (blessings and peace of Allah be upon him) said: “Whoever says in the morning and the afternoon: ‘Allahumma inni asbahtu ushhiduka wa ushhidu hamalata ‘arshika wa malaa’ikataka wa jamee‘a khalqika annaka anta Allahu laa ilaaha illaa anta wa anna Muhammadan ‘abduka wa rasooluka (O Allah, on this morning and I call upon You and I call upon the bearers of Your Throne, Your angels and all of Your creation to bear witness that You are Allah, there is no god worthy of worship except You, and that Muhammad is Your slave and Your Messenger),’ Allah will ransom one quarter of him from the Fire. Whoever says it twice, Allah will ransom half of him from the Fire; whoever says it three times, Allah will ransom three quarters of him from the Fire; and whoever says it four times, Allah will ransom him from the Fire.” (Lataa’if al-Ma‘aarif p. 283).
This immense virtue should motivate one to be keen to do more good, and should deter one from being lethargic or too lazy to do acts of worship and obedience or from wondering about this reward and virtue and thinking that it is unlikely.
And Allah knows best.