Praise be to Allah.
The scholars differed as to the minimum length of time for i’tikaf .
The majority of scholars are of the view that the minimum length of time is a moment. This is the view of Abu Hanifah and Ahmad. See al-Durr al-Mukhtar (1/445); al-Majmu’, 6/489; al-Insaf, 7/566.
Al-Nawawi said in al-Majmu’, 6/514:
“With regard to the minimum length of time for i’tikaf , the majority stipulated that it must be observed in the mosque, and that it is permissible to do a lot or a little, even an hour or a moment.”
They quoted several reports as evidence for that:
1 – That i’tikaf in Arabic means staying, and the word may be applied to a long period of time or a short one; there is no report in shari’ah that defines it as being a specific length of time.
Ibn Hazm said:
“I’tikaf in the language of the Arabs means staying… any stay in the mosque for the sake of Allah with the intention of drawing closer to Him is i'tikaf… whether that is for a short time or a long time, because the Quran and Sunnah do not specify any number or length of time.” Al-Muhalla, 5/179
2 – Ibn Abi Shaybah narrated that Ya’la ibn Umayyah (may Allah be pleased with him) said: I will stay in the mosque for an hour, and I am only staying to observe i’tikaf. Ibn Hazm quoted this as evidence in al-Muhalla (5/179); it was quoted without comment by al-Hafiz in al-Fath. “Hour” here refers to a period of time but it does not mean an hour in the modern sense of sixty minutes.
Some scholars are of the opinion that the minimum length of i'tikaf is one day. This was narrated from Abu Hanifah and was the view of some of the Malikis.
Shaykh Ibn Baz said in Majmu’ al-Fatawa (15/441):
“I’tikaf means staying in the mosque to worship Allah, whether that is for a long time or a short time, because as far as I know there is no report to indicate a set time, whether one or two days or more. This is an act of worship which is prescribed in Islam unless one vows to do it, in which case it becomes obligatory. This applies equally to men and women.”
And Allah knows best.