إِنَّ مَحَلًّا وَإِنَّ مُرْتَحَلًا
There is indeed a stay, and there is indeed a departure.
«مَحَلًّا» denotes settling or lodging; «مُرْتَحَلًا» denotes departure. Each is an accusative noun governed by «إنّ», while the relevant predicate is unexpressed.
An explanatory reconstruction is إِنَّ لَنَا فِي الدُّنْيَا مَحَلًّا، وَإِنَّ لَنَا عَنْهَا إِلَى الْآخِرَةِ مُرْتَحَلًا.
«لَنَا» completes the predication, while the references to this world and the afterlife clarify the intended contrast; these additions are an analytical reconstruction, not quoted words from the verse. Brevity preserves metre and sets lodging against departure without obscuring the contrast.