We have already stated in the answer to question no. 13973 that selling something by installments for a higher price is permissible.
Although it is permissible, we should not be too lax on this matter, especially if there is no need for it, because buying by installments means buying with debt, and we should not be too lax when it comes to taking loans; rather we should not seek loans unless there is a need for it and it is essential.
The Prophet (peace and blessings of Allaah be upon him) used to seek refuge with Allaah from debt.
Al-Bukhaari (833) narrated from ‘Aa’ishah (may Allaah be pleased with her) that the Messenger of Allaah (peace and blessings of Allaah be upon him) used to make du’aa’ in his prayer and say, “Allaahumma inni a’oodhu bika min ‘adhaab il-qabr, wa a’oodhu bika min fitnat il-maseeh il-dajjaal, wa a’oodhu bika min fitnat il-mahya wa fitnat il-mamaat; Allaahumma inni a’oodhi bika min al-ma’tham wa’l-maghram (O Allaah, I seek refuge with You from the torment of the grave; I seek refuge with You from the fitnah of the Dajjaal; I seek refuge with You from the trials of life and death; O Allaah, I seek refuge with You from sin and debt).” Someone said to him, “How often you seek refuge with Allaah from debt!” He said, “If a man gets into debt, he speaks and lies, he makes a promise then breaks it.” And he (peace and blessings of Allaah be upon him) used to call on people to pay off debts.
The Prophet (peace and blessings of Allaah be upon him) also used to say in his du’aa’: “Allaahumma anta al-awwal fa laysa qablaka shay’un, wa anta al-aakhir fa laysa ba’daka shay’un, wa anta al-zaahir fa laysa fawqaka shay’un, wa anta al-baatin fa laysa doonaka shay’un, iqdi ‘anna al-dayn wa aghnina min al-faqr (O Allaah, You are the First and there is nothing before You, You are the Last and there is nothing after You, You are the Most High and there is nothing above You, and You are the Most Near and there is nothing closer than You. Settle our debt for us and spare us from poverty).”
Hence no one should buy by installments when he is able to pay the whole price immediately, because then he is getting into debt when he has no need to, and he is exposing himself to danger, because if a person dies in debt he will not be forgiven, even if he dies as a shaheed on the battlefield, until his debt is paid off.
Muslim narrated (1886) from ‘Abd-Allaah ibn ‘Amr ibn al-‘Aas that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “The shaheed will be forgiven for every sin except debt.”
And al-Nasaa’i narrated (4605) that Muhammad ibn Jahsh (may Allaah be pleased with him) said: We were sitting with the Messenger of Allaah (peace and blessings of Allaah be upon him) when he raised his head towards the sky, then he put his palm on his forehead and said: “Subhaan-Allaah! What a strict issue has been revealed to me!” We remained silent and were afraid. The following morning I asked him, “O Messenger of Allaah, what is this strict issue that has been revealed?” He said, “By the One in Whose hand is my soul, if a man were killed in battle for the sake of Allaah, then brought back to life, then killed and brought back to life again, then killed, and he owed a debt, he would not enter Paradise until his debt was paid off.” Classed as hasan by al-Albaani in Saheeh al-Nasaa’i, 4367.
The point is that if you are well off and you do not need the money you have, and you think it most likely that you will not need it in the near future, then it is better for you to pay cash and not to purchase by installments.
And Allaah knows best.