Abu Ubayd (may Allah have mercy on him) said: the Prophet (peace and blessings be upon him) was asked: Whose testimony is acceptable in (matters of) fosterage? He (peace and blessings be upon him) said: "The testimony of one man or one woman." This is a weak chain; a chain like this cannot be taken as proof. Muhammad bin Uthaym is accused of lying, and Ibn al-Baylamani is weak, and there is disagreement from him regarding its text: it is said like this, it is said "one man and one woman," and it is said "one man and two women." And Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرضاع / 15677