Those who said: if he resolves to stay fifteen days, he prays in full

Sa'id bin al-Musayyib said: When a traveller resolves to stay fifteen days together, he will pray the full prayer.

Sayyiduna Ali (may Allah be pleased with him) said: When you intend to stay ten days, pray the full prayer.

Likewise (through another chain).

Abu Ja'far said: When one intends to stay ten days, he should pray the full prayer.

Abu Ja'far used to pray the full prayer when he intended to stay ten days.

Mujahid said: When Sayyiduna Ibn Umar (may Allah be pleased with them both) resolved to stay fifteen days, he would release his mount to graze and pray four rak'ahs.

Sa'id bin Jubayr said: When you are to stay more than fifteen days, pray the full prayer.

Sa'id bin al-Musayyib said: When you are to stay four days, pray four rak'ahs.

Abu Hakimah said: I asked Sa'id bin al-Musayyib about this, and he said: When you are to stay three days, pray the full prayer.
Waki' said: I heard Sufyan say: If he resolves to stay fifteen days, he prays the full prayer from the time he enters; and if he does not know when he will leave, he prays two rak'ahs even if he stays a year.

And that is the view he held.