put all one's eggs in one basket
Risk all of one's resources in a single venture, as in He had warned Peter about investing heavily in a single stock; it was putting all his eggs in one basket. This proverb, first recorded in 1710, has largely replaced the much older trust all one's goods to one ship. Mark Twain played on it in Pudd'nhead Wilson (1894): "The fool saith, 'Put not all thy eggs in one basket' ... but the wise man saith, 'Put all your eggs in one basket, and watch that basket!'"