Sayyiduna Ibn Mas'ud (may Allah be pleased with him) said: "Beware of saying again and again, 'What if it were so?', for those before you were destroyed only because of their abundance of 'What if it were so?'. And do not draw analogy between one thing and another, lest a foot slip after being firmly planted. And when one of you is asked about something he does not know, let him say: 'I do not know,' for that (saying) is one third of knowledge."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8518