It is narrated from Sayyiduna Ali (may Allah be pleased with him) that when a man becomes junub (in a state of major ritual impurity) while travelling, he should wait until the last part of the prayer time; then if he does not find water, he should perform tayammum and pray.
Al-Harith al-A'war is not used as evidence.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1101