Maliks Muwatta Book 9, Hadith Number 18.

Section : The Prayer of a Traveller when Undecided whether to Remain in a Place or Not.

Yahya related to me from Malik from Ibn Shihab from Salim ibn Abdullah that Abdullah ibn Umar used to say, “I pray the prayer of a traveller as long as I am undecided whether to remain somewhere or not, even if I am detained for twelve nights.”