Abu Hanzalah says that I asked Sayyiduna Ibn Umar (may Allah be pleased with them both) about the prayer during travel. He replied: "The prayer during travel is two rak'ahs, and this is the Sunnah of the Prophet (peace be upon him)."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5213
Hadith Gradingحکم دارالسلام:صحيح لغيره ، وهذا إسناد محتمل للتحسين من أجل أبي حنظلة .