Abu Humayd al-Sa'idi (may Allah be pleased with him) narrated that the Messenger of Allah (peace and blessings be upon him) set out on a campaign. When he had gone beyond Thaniyyat al-Wada', he saw a detachment and asked: "Who are these?" People said: These are the people of Banu Qaynuqa', and they are the clan of Abdullah bin Salam (may Allah be pleased with him). He (peace and blessings be upon him) asked: "Have they accepted Islam?" People said: No, rather they are on their religion. He (peace and blessings be upon him) said: "Tell them to go back; we do not seek help from polytheists."
This chain is more authentic.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17878