Jesus "sighed deeply in His spirit," and, turning from the group of cavilers, re-entered the boat with His disciples. In sorrowful silence they again crossed the lake. They did not, however, return to the place they had left, but directed their course toward Bethsaida, near where the five thousand had been fed. Upon reaching the farther side, Jesus said, "Take heed and beware of the leaven of the Pharisees and of the 408 Sadducees." The Jews had been accustomed since the days of Moses to put away leaven from their houses at the Passover season, and they had thus been taught to regard it as a type of sin. Yet the disciples failed to understand Jesus. In their sudden departure from Magdala they had forgotten to take bread, and they had with them only one loaf. To this circumstance they understood Christ to refer, warning them not to buy bread of a Pharisee or a Sadducee. Their lack of faith and spiritual insight had often led them to similar misconception of His words. Now Jesus reproved them for thinking that He who had fed thousands with a few fishes and barley loaves could in that solemn warning have referred merely to temporal food. There was danger that the crafty reasoning of the Pharisees and the Sadducees would leaven His disciples with unbelief, causing them to think lightly of the works of Christ.

Jesus "sukkede dybt i sin ånd", og han vendte sig fra denne kreds af smålige kritikere og gik igen i båden sammen med sine disciple. I sorgfuld tavshed satte de atter over søen. De vendte imidlertid ikke tilbage til det sted, hvor de var kommet fra, men stilede lige mod Betsajda, i nærheden af det sted, hvor de fem tusinde var blevet mættede. Da de var nået over til den anden side, sagde Jesus: "Se til, at I tager jer i vare for farisæernes og saddukæernes surdej!" Jøderne havde fra Moses tid været vant til at fjerne surdej fra deres hjem i påsketiden, og derfor havde de lært at betragte den som et billede på synd. Alligevel misforstod disciplene Jesus. Ved den pludselige afrejse fra Magdala havde de glemt at tage brød med, og de havde kun et eneste brød. De mente, at det var dette, Kristus hentydede til, og at han advarede dem mod at købe brød af en farisæer eller en saddukæer. Deres mangel på tro og åndelig indsigt havde ofte fået dem til at misforstå hans ord på lignende måde. Nu dadlede Jesus dem, fordi de mente, at han, som havde mættet tusinder med nogle få fisk og bygbrød, med denne højtidelige advarsel kun havde hentydet til timelig føde. Der var fare for, at farisæernes og saddukæernes snedige ræsonnementer kunne smitte disciplene med vantro, så de kom til at undervurdere Jesu undergerninger.